According to Man/boy love and the American gay movement Journal of Homosexuality (a peer-reviewed journal) volume 20, issues1-2, pages 251-274 (1991):
Firstly, it is stated that author David Thorstad was the president of "New York's Gay Activists Alliance" and "a founding member of the North American Man/Boy Love Association (NAMBLA) and of New York's Coalition for Lesbian and Gay Rights (CLGR)".
New York's Gay Activists Alliance (GAA), successor to the Gay
Liberation Front and a prototype activist group founded in December 1969, opposed legal restrictions on sex based on age, although
this was never a focus of the group's activities. [footnote 2] In 1976 GAA became the first gay group in New York — and probably in the country — to sponsor a public forum on man/boy love. Held at the Church of the Beloved Disciple on April 4, the forum brought together a "panel of pederasts" to speak on the topic "Of Men and Boys: Pederasty and the Age of Consent."
The Canadian Lesbian and Gay Rights Coalition, a cross-Canada
group, also favored abolishing the age of consent. Many activists
shared the view that the state had no business regulating sex between consenting partners, whatever their age.
...
MAN/BOY LOVE HITS THE GAY MOVEMENT
In 1977, the issue of sex between adults and minors moved
abruptly to center stage. Anita Bryant began to articulate the mounting backlash to gay liberation by zeroing in on a perceived weak
link: the widespread belief that gay men seduce young boys and
turn them into queers. The name of her organization — Save Our
Children— transparently implied this.
Simultaneously, a new hysteria about "kiddie porn" arose, fed
by the political right and the feminist movement, with unmistakable
suggestions that gay men who loved boys were in reality exploiting
and abusing them. This clever propaganda ploy not only deftly exploited the public's ignorance about homosexuality, but also caught
the gay movement off guard: It was unprepared to make an intelligent rebuttal. Pederasty was a secret not to be told. Yet although
man/boy love represented a minority phenomenon within the gay
subculture, it was far from unusual. [footnote 3]
The gay movement went into a defensive mode. "Oh, no, homosexuals don't do that. Most child molestation is by heterosexual
men against little girls."
...
Boy-lovers began to organize for the first time, in response to
two widely publicized incidents in December 1977. Following the
arrest of 24 men in Revere, Massachusetts, for consensual sex with
boys (mostly teenagers), the Boston-Boise Committee was formed.
Its goal was to educate the media and public about the issues in
volved. A few weeks later, the Body Politic, a Canadian gay liberation newspaper, was raided by the police because it had published
an article entitled "Men Loving Boys Loving Men." [footnote 4]
On December 2, 1978, 150 persons attended a conference on "Man/Boy Love and the Age of Consent" in Boston's Community Church. Initiated by Tom Reeves of the Boston-Boise Committee, several participants were prominent in the gay and progressive movements, which gave the issue a new urgency. Afterwards, 30 boy-lovers and youth formed their first activist organization, the North American Man/Boy Love Association (NAMBLA). Boy-lovers and gay youth were becoming active protagonists.
The fact that boy-lovers had come out of their closet within a closet immediately embroiled the gay movement in controversy. Gay Community News' first 1979 issue published my "Statement to the Gay Liberation Movement on the Issue of Man/Boy Love," which challenged the movement to return to a vision of sexual liberation. It argued that "the ultimate goal of gay liberation is the
achievement of sexual freedom for all — not just equal rights for lesbians and gay men/ but also freedom of sexual expression for young people and children." It criticized the movement for "limiting itself to a turf restricted to consenting adults" and behaving "as though sex had nothing— or little — to do with our struggle." It urged the movement not to limit its demands "to those thought acceptable to a frightened status quo." [footnote 5]
This "manifesto" set off a debate that lasted several months.
Much of the lesbian response was hostile and buttressed with arguments like "lesbians don't do that." But a piece by one lesbian
feminist stood out for its sensible treatment of a topic heretofore
passed over in silence: woman-girl love. Beth Kelly's "On
'Woman/Girl Love' -Or, Lesbians Do 'Do It'" noted that the ignorant reactions of many lesbians to man/boy love had helped her to understand "what it could mean to know that your most intensely private moments were nothing more than threads in the widely woven fabric of political experience that enfolds us all." A lifelong lesbian, she acknowledged being involved in cross-generational
love "as a girl and as a woman." She described her sexual love for
her great-aunt — more than 50 years her senior— when she was between eight and eleven years old. She summarized her journey to self-acceptance:
It has always seemed to me that people know when sex is a
right thing for them to be doing, when mutually consented to,
regardless of who else may or may not share or understand that
...
THE 1979 MARCH ON WASHINGTON
The man/boy love issue again surfaced early in 1979 at a national
conference in Philadelphia which called the historic gay march on
Washington, DC, set for October 14. On February 25, the conference adopted the Gay Youth Caucus proposal for a demand urging "Full Rights for Gay Youth, including revision of the age of consent laws." At a meeting of the group's newly elected National Coordinating Committee, held as soon as the conference had adjourned, lesbians threatened to split (thereby sabotaging the march)
unless a substitute for the Gay Youth Caucus demand was adopted.
It was. The substitute— which was drafted by an adult lesbian and subsequently approved by a majority of the delegates in a mail poll (a favorite technique of the trade-union bureaucracy to prevent rank-and-file organization) — read: "Protect Lesbian and Gay Youth from any laws which are used to discriminate against, oppress, and/or harass them in their homes, schools, jobs and social environments." [footnote 7]
The committee explained its action as a desire "to officially
adopt this statement to replace and enlarge the concept of the 'Revise the Age of Consent' motion in such a way as we believe to have been the broad meaning and will of the body. ..." It substituted the concept of "protecting" gay youth, suggesting that they needed to be "protected" from choosing the wrong kind of lovers (i.e., gay men). It served to confuse rape or coercive sex with consensual sex and love. It suggested that age-of-consent laws protect
young people from unwanted sex, when in reality they do just the
opposite -they punish only sex that is consensual, on the grounds
that the younger partner is incapable, by virtue of age, of giving
consent, even when it is not disputed that consent was given!
I was one of a small minority of delegates who refused to go
along with the substitute statement and protested the undemocratic
process whereby it was pushed through. The substitute was ageist, I
argued, since it was written from an adult's point of view. Its notion
of "protection" "smacks of Anita Bryant and motherhood."
Moreover, "You don't protect a gay youth by sending his/her older
lover to jail and by dragging the young person into Family Court, or
worse. ... Our goal should be sexual freedom, not continued restrictions on consensual sexual activity." [footnote 8]
In March 1979 lesbians in New York's Coalition for Lesbian and
Gay Rights successfully brought a motion labeling the age-of-consent issue "divisive." Lesbian Feminist Liberation (LFL) issued a
news release accusing "so-called Man/Boy Lovers" of attempting to legitimize sex between children and adults by confusing the real needs of Gay youth with a call to repeal all age of consent laws. Feminists easily recognize this as the
latest attempt to make palatable the sexual exploitation of children.
It called the age-of-consent issue "a diversion," and put the coalition on record opposing "the sexual abuse of children by heterosexual or homosexual persons" -thereby implying that boy-lovers were guilty of "sexual abuse." It also sounded a note of censorship:
we will not passively march alongside pederast banners or
signs, nor quietly stand and listen to pederast speeches at any
march or rally. Lesbian Feminist Liberation will not support
pederasts within the Lesbian and Gay movements nor anywhere else. [footnote 9]
LFL's position suggested hostility to males. It did not go far
enough, however, for the Socialist Workers Party (SWP), whose
delegate to the CLGR proposed that the group adopt a formal position "for the protection of male and female children from sexual
abuse by adults." He argued that "adults having sex with children
is exploitation and is the antithesis of the fight for lesbian and gay
rights." He added, "I am not for giving children the right to consent to sex." His motion was overwhelmingly defeated and a substitute passed expressing "opposition to the sexual abuse of children by homosexual or heterosexual people." The SWP thereupon withdrew from the coalition and from the gay movement, and went on to lobby women's groups not to participate in the October march on Washington, in part because the organizers were allegedly
"soft" on child exploitation!
...
The controversy continued to simmer. On April 1, 1980, following a heated debate, the CLGR decided to call for my removal as a kevnote speaker at a gay rights rally on the steps of the state capitol in Albany. Although the effort failed, it did result in most lesbian groups boycotting the demonstration. A half dozen of the most active groups in the coalition resigned.
Later that month, a few lesbians attempted, in vain, to persuade
NAMBLA to leave a march in New York City protesting a mobilization the same day by the Christian right wing in Washington, DC. Mark Moffet, a 15-year-old speaker from Gay Youth of New York at the rally in Sheridan Square that ended the march, defended the right of boy-lovers to participate in the movement. He was booed by a claque from NOW -the only time I have seen presumably straight supporters boo a gay speaker at a gay rally.
Two months later, a group calling itself the "Lesbian Caucus- Lesbian & Gay Pride March Committee" tried to split the annual New York City Gay Pride March on June 29. It distributed a leaflet calling on women to split from the march on the false grounds that the organizing committee "has been dominated by the Revolutionary Socialist League, the North American Man/Boy Lovers Association [sic] and their supporters." At the entrance to Central Park, they tried to divert people away from the official rally to a separate event. No address or phone contact appeared on the leaflet. A special issue of Semiotext(e) on "Loving Boys," an important contribution to the growing debate, and now an underground classic, was distributed at the march. [12]
...
In 1984 the debate on man/boy love shifted to the West Coast. In
San Francisco, efforts to remove NAMBLA from the annual Lesbian/Gay Freedom Day Parade failed, as they had in New York.
NAMBLA's October 1984 convention in San Francisco's Pride
Center included a public panel discussion on "Man/Boy Love and
Sexual Liberation" with Mattachine Society founder Harry Hay;
Jim Kepner, curator of the International Gay and Lesbian Archives
in Los Angeles; Morris Kight, long-time gay rights and social activist from Los Angeles; Jes Harrison, a 16-year-old gay youth; and me. The participation of Hay, Kepner, and Kight was welcome support from activists whose credentials went back to the beginnings of the U.S. gay movement.
...
As part of the internal debate within the gay community, the following is a statement from the Chicago Stonewall Committee, as published in the 26 March 1983 Gay Community News [emphasis in original text]:
...Who belongs in the gay movement, and who decides?
We think s/m lesbians and NAMBLA do belong. The gay movement is based on expanding people's options, in bed and out, not on setting some new sexual “party line.” Not too long ago, the whole gay issue was too kinky to be taken seriously as a progressive social movement. In the particular cases mentioned above, NAMBLA and the s/m women were only seeking places to talk about their sexual preferences. We certainly support their right to act on them as well,
See also the 1992 The Responsive Community, which says:
The annual Gay Pride March in New York, on the other hand, allows NAMBLA to participate because the march does not exclude any organization seeking to celebrate gay liberation by marching
Also, according to the Encyclopedia of Homosexuality (1990):
During the early eighties at the New York Gay Pride marches, gay anarchists, S/M groups, gay atheists, NAMBLA, Fag Rag and others all marched together with banners
A 1993 article in Ten Percent says:
Since its formation, NAMBLA, like other fringe groups, has lived on the edge of the lesbian and gay community, occasionally finding a sympathetic ear in gay publications, sometimes listed in gay directories, and wafting in and out of gay pride parades (NAMBLA has been allowed to march under its own banner in New York, San Francisco, Boston, and last year's March on Washington).
In summary, NAMBLA did march in some, but not all, gay pride parades in 1979 and the 80s. Initially, they were somewhat welcomed by the male gay leadership, however opposition arose from women.
As a counter-example, NAMBLA was excluded from a 1986 Los Angles gay parade, and Harry Hay, one of the early leaders of the US gay rights movement, wore a "NAMBLA WALKS WITH ME" sign in protest of their exclusion.

(photos by Sandy Dwyer, also in Trouble with Harry Hay Founder of the Modern Gay Movement, Stuart Timmons, 1990)