[ZenGum]

It is true that sometimes there are riots where strong police force is necessary, and a well equipped riot squad (or well-armed SWAT team) is called for.

Problem is, once that squad exists, it wants to find something to do. And the powers that be seem quite keen to use that sort of force even when it really isn't called for. As Bruce said, this alienates the majority of people and makes the cops the enemy.

Last year I saw a doco which talked about dealing with the riots at the Celtics Vs Rangers games in Scotland. Step one was to make one set of entrances for Celtics fans, and the other set of entrances for Rangers fans, but they were within sight of each other and just a bottle's throw apart.
If the gap in between was filled with fully equipped riot cops, things almost always turned violent. Instead they now fill the gap with ordinary cops in uniform, and things almost always remain peaceful. They do, of course, have a few truckloads of riot cops in a warehouse a short distance away.