Edit: Ouch, looks like quite a few people here do. Do y'all really think that's the best way to effect social and political change? A minority of Americans screaming louder and using terrorism to vent their spleens won't solve the issue. In a democracy, everyone must focus on getting more people to vote for different policies to effect change.
If it makes you feel a little better about the world, I downvoted you because I thought you were wrong that no one supports this, not at all because I support burning police cars. I've definitely seen lots of support online that accepts the destruction of police (aka public) property as a legitimate (or at least expected) form of protest, and am surprised that you haven't. So yes, there are supporters, but possibly not quite as many as it would first appear.
However, I haven't really seen others support it, aside from the obvious lunatics on television (many of whom simply want to grab free stuff). I'm not sure which sites I'd have needed to frequent to see such support, but I'm always looking to expand my knowledge base, so would appreciate a few recommendations.