I agree the draft and particularly its annual or semi-annual lotteries played a big part in the anti-War movement, just as the French Resistance got a huge shot in the arm from the Vichy Government's S.T.O. program (Service du Travail Obligatoire) drafting French youth for labour in bomb-wracked German factories. Young people tend to resist dragnet programs which force them into life-threatening situations for no good purpose. At some point in the 1970s the draft program was modified by assigning priority numbers at random to all the 366 possible birthdays of draft-age males. Everyone knew from the number assigned to his birthday whether or not he was guaranteed a ticket to Nam or whether he had good reason not to fear, regardless of when he would turn 18. This drastically reduced the number of self-interested protestors, because where previously everybody stood an equal chance of being drafted by lottery, now there was a huge cohort of draft-age males certain that their own numbers would never come up.
The Viet Nam war was objectionable for perfectly good moral reasons NOT related to self-preservation, though. I think once students found their way into the anti-war movement, they would have tended to stay even after the draft was "reformed" and their own personal draft numbers posed no danger to them. They could hardly drop out of the Movement at that point because it would be admitting to the cowardly motivation that led them to protest in the first place.
Bottom line is we don't know how many anti-War people signed up out of self-preservation and how many for reasons having nothing to do with self-preservation. The war was a huge on-going atrocity, one that by Nuremburg standards would obviously have earned its perptrators a place on the gallows, and so I think it's overly simplistic to think that all protestors were motivated by self-preservation. That is a view that's extremely insulting to the American people.
