What it comes to is that there isn't a good choice. Look at it from the street cop's point of view. You may think, watching television, that the cops have the advantage, that they're the bullies. They have teargas and guns and all. It's not quite like that.
Riots are scary.
The cops are in fact outnumbered, however blue their uniforms may be. It takes getting hit about once by a bottle with many hostiles around and your adrenaline sluices loose and your blood pressure goes way up. It gets real easy to smack people. And it would for you, too, gentle reader. The problem is much more the situation than it is the cops.