The story in question was originally attributed not to an anthropologist, but to a childhood memory!
Consider the Babemba tribes of southern Africa, where the social structure includes only an elementary criminal code. Apparently, the lack of
fixed rules to enforce justice stems from close community living, which
never made such laws necessary. Brian Sharpe, our red-bearded friend, and director of the William Roper Hull Progressive Education Center, Calgary, Canada, was reared by the Babemba for the first nine years of his life. He passed the following information on to us, along with the tribal method of handling antisocial, delinquent, or criminal behavior, which were exceedingly infrequent.
When a person acts irresponsibly or unjustly [...] The person in the center, we can only suppose, experiences a variety of feelings about his misdeed, having been flooded with the charitable warmth of his acquaintances, friends and loved ones. Perhaps this overwhelming positive bombardment not only strengthens his positive self-image, but also helps him choose to live up to the "expectations" of his tribe.
Leonard and Natalie Zunin, Contact: The First Four Minutes. Ballantine Books, 1979. Emphasis added.
One interesting aspect of this story is that the tribe in question is called the Bemba tribe, not the "Babemba tribe." Babemba means "the people of the Bemba tribe." I searched throughout ethnographic accounts of the Bemba tribe available in my university library but could find no discussion of such a practice other than references to the book Contact: The First Four Minutes.
Who was Brian Sharpe and where did he grow up? A marriage announcement in the Calgary Herald of September 14, 1968 states that Francis Noel Brian Sharpe's father "Noe [sic] Sharpe" immigrated from Salisbury, Rhodesia. This is likely the Noel Sharpe who is said in the Geological Society of Zimbabwe newsletter to have worked for a firm named "Mineral Search of Africa"; a 2004 article "Emerald mineralization in the Kafubu area, Zambia" shows that firm was mining there "in the 1940s and 50s," which matches the dates when Brian Sharpe was in college writing a 1963 thesis on social work. This evidence suggests a childhood spent near a copper mine in rural Zambia, home to a people called the Lamba, who speak the Bemba language.
An article about the 21st century Lamba people states that disobedient children are sent to live with an elder:
Naughty children or children not conforming to the norms at an
expected stage are taught alone in a particular context by a person in
the community perceived to have the skills of coping with such
behaviour. This teacher could be an uncle, aunt or another relative.
After all, the Lambas argue they are all related. The child is then
sent for a period of time to live with him/her so as to learn from
Kalenga, Rosemary C., Vitallis Chikoko, and Fumane Khanare. "Leadership practices among the Lamba people of Zambia: some implications for school leadership." Indilinga African Journal of Indigenous Knowledge Systems 12.2 (2013): 231-241.
Could Sharpe have misremembered some other practice, or was he raised by another Bemba-speaking tribe? (Why did he refer to the tribe as "Babemba" instead of Bemba or Lamba?) To answer this, I emailed a Bemba tribe member: Dr. Richard Mukuka, a professor at the University of KwaZulu-Natal in South Africa. Here is his reply:
There are two references to "Bemba". First, the Bemba ethnic group which (according to the 2010 population census of Zambia) constitutes 21% of the Zambian population. Second, the Bemba-speaking people who (according to the same census) constitute 33.5% of the Zambian population. There are 73 ethnic groups in Zambia. I'm a native of the Bemba ethnic group.
A person who acts irresponsibly or unjustly (for the Bemba ethnic group) is only rebuked and corrected by his/her seniors who have the moral duty to "parent" and morally align the wrongdoer. Depending on the the social position of the wrongdoer, the seniors can be varied. The juniors and minors cannot correct their senior. If juniors notice a wrongdoing of their senior, they will recruit the help of someone senior to the wrongdoer: senior community members, village head persons, or the king in council. The practice you've described is not practiced by the Bemba people or any Bemba-speaking people I know.
With kind regards,
I hope this resolves the question to your satisfaction.
You can read more about actual ubuntu practices of the baBemba in this article by Dr. Mukuka, available for free on JSTOR:
Mukuka, Richard. “Ubuntu in S. M. Kapwepwe's ‘Shalapo Canicandala’: Insights for Afrocentric Psychology.” Journal of Black Studies, vol. 44, no. 2, 2013, pp. 137–157.