I watched it happen. Did you?
There were goddam impromptu PARTIES on my campus when those helicopters were pushed off of aircraft carriers. In the student union. In some cases, with faculty members. The retreat from Vietnam was the high point of the leftist movement in America, although with their major cause gone, they soon lost a lot of their enthusiasm.
I swear some of you must live in a parallel universe of some kind. Next you'll tell me nobody on the Left celebrated when Nixon resigned.