Because I knew conservative professors who taught then, and they attested to it. The subject came up about other radical professors when discussing Morris Starsky at Arizona State:
http://en.wikipedia.org/wiki/Morris_Starsky
There were several such agitators in the California universities as well, and they were not bashful about using students as their pawns.
But this leads to the question, why are you defending such scoundrels? Though you did not personally experience their venom is certainly no evidence that others did not.
By the way don't start lying about me because you made some stuff up, I'm not defending anyone, you posted something that you were trying to pass off as actual history and I was there and never saw it and never heard of those actions, did you? If you want to talk about leftist professors fine but don't start making up the details as though they were history.
Though the odds were quite small of being drafted, being sent to Vietnam, and dying, students were threatened that if they *didn’t* protest against the war, their professors would fail them, they would lose their draft deferment, be drafted, sent to Vietnam, and die.