Lembcke has published a number of articles asserting many times that this is a myth, so it is probably helpful to cite another writer on the same subject. Bob Greene, in his book Homecoming (1989), collected many anecdotes of supposed spitting incidents, solicited through a national newspaper column. However, he collected just as many letters from Vietnam veterans insisting that such anecdotes were false and created after the fact for reasons that all veterans knew. (DavePhD's answer includes the only eyewitness accounts of bystanders spitting on Vietnam veterans published during the war, but both of the two articles descibe war supporters spitting on anti-war veterans.)