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.
I'm reluctant to give my best recommendation, because it's a fragile community, but hopefully this thread is far enough along that it doesn't have a lot of traffic at this point.
Currently, the discussion at http://slatestarcodex.com is the best that I've found on the internet for hearing intelligent views from people I otherwise disagree with. The "open threads" are very long, and contain a lot (50%?) of dross, but there are also a lot of gems within them. Post-Floyd, I was surprised by how many people whose opinions I generally respect were at least conditionally supportive of burning the police precinct office in Minneapolis.
If you are interested in this question, you could pose it there. It would be considered "culture war", and thus only acceptable in the "fractional" open threads. That is, the ones that end with ".25", ".5", or ".75". To reduce visibility, these aren't officially listed on the front page, but are available from the Recent Posts or from the Archives link. Create an account, post the question there in as fair and open-ended a manner as you can, and I think you'd get good responses.