It seemed that for all its bluster, the fifth columnists, the anarchists, and the marxist brownshirts stayed far, far away from the 4/15 rallies. The few who went were very quickly identified and forcibly removed.
If I am at a rally where the antagonists become violent, I will deal with their actions in an appropriate fashion. I would suspect that there are a great many others who feel the same way.
There has been little violence because zero still has an approval rating above 40%. If he is behind in the polls in 2012 we will see scenes reminiscent of 1968. Guaranteed.