Breja: If the game actually had the option of customising the rioters and the police to be whoever you feel like (Nerds vs Bothered About Dungeons & Dragons! Hippies vs FBI! Vegetarians vs McDonald's security!) it would be a way smarter than game than it is right now.
I've imagined a game somewhat like this. You create an FPS game, where you run around shooting people. The hook is that there's a website for the fan community full of their own created textures, which people can download and use for the enemies. So if you want to shoot purple people, or joggers, or aliens, or nazis, or moms-wheeling-carriages, or whatever, you just dl the texture.
Everyone can then kill whatever types of enemies they want, and because the textures would be fan made, the devs "shouldn't" be held liable.