I've tried making this point before, but you've made it in a way I've always failed to. When police approach a situation fulfilling the role of the individual ready to respond to an incident, it almost seems like a self-fulfilling prophecy.
Yes. I've seen this happen myself. In college, after some sportsball event, everybody poured out into the streets, milling around, chatting, celebrating. As soon as the police started to try to make everybody go home, suddenly there was a focus. They created an oppositional dynamic all by themselves, and from there it escalated.
The next day, the papers were of course full of reports of badly behaved crowds and near-rioting stopped only by dedicated law enforcement officers. That's definitely not what I saw.
