As I see it, a few protestors become rowdy agressive assholes, put the cops in a panicked, backed-into-a-corner, insinctive survival mindset, and the whole crowd pays the price for the actions of a few assholes. It's not right for the cops to brutalize people, but then it's not right for a bear to tear apart a guy that accidentally walked into it's lair.... just try telling the bear that.