I don't envy the police in this. There are vile people exercising their 1A rights in a deliberately provocative but lawful way being opposed not just by the majority, the decent people, in an equally lawful way, but also by violent thugs who have decided "vile words equal violence" and thus have a contrived moral justification to use actual physical, preemptive violence in response. The police need to enforce the limits of parade permits to the letter to keep the vile first group contained and away from the decent second group, and act swiftly to isolate and counter the third to keep the peace.