I won' speak for him but I have a few thoughts.
I think the whole thing is absurd. The officer most likely acted in self defense and even if not Brown clearly attacked the officer at one point and he was clearly a thug. The evidence seems to back up the officer's story. The initial eye witness reports are full of problems and there were other eye witnesses (I'm assuming they were black) who backed up the officer. I think the lynch mob mentality is very dangerous. Frankly if black people want to protest unfair treatment and police brutality there are plenty of better cases to hang their hats on. It's odd they picked this particular one.
Rioting and looting is simply antisocial behavior. I would be embarrassed if I were black. The people who will pay the price are the Ferguson residents themselves - especially the ones too poor to get out. It takes decades for some areas to recover from major riots and the rioters are only hurting themselves.
I don't know that you can say this is the left vs the right. I'm sure plenty on the left agree with you and me on this one. That being said I'm left on about 70% of issues and right on about 30%.
As for participation bias, I doubt there are many people here who don't do it. Sometimes it just boils down to what issues really chap your hide...