I am no fan of that Nazi bunch, but, they had a permit to march, they were abiding by the law. If they did not abide by the law it is up to the police to rectify the situation.
The looters and vandals broke the law. They should have all been rounded up and thrown in jail, made to pay fines and make restitution. There is NO excuse for what those people did.
Those looters and vandals were just looking for an excuse to riot, and the Nazis provided it. A pox on both of their houses.