Being alive at the time, I remember there was a lot of demonizing one's opponents, much like today in fact. I remember anti-war protestors being thought of as free love fornicating, pot smoking, communists and police and soldiers being called pigs and baby killers.

Once your opponent is dehumanized in this way, the violence that follows is easily justified, certainly in the heat of the moment. It becomes easy to throw rocks at police and burn ROTC buildings. It becomes easy to shoot protestors who are enemies of the state.