I think another reason for the protests are, simply put, protests can be fun. You get attention, news cameras, crowds chanting. The exhilaration, excitement of a purpose, and feeling of 'we are gonna change the world!'
Some people protest just for the sake of protesting.
Well, I think most of the community there (and elsewhere) realizes things are 'broken' in black culture - but it's easier to blame other people for it than to accept responsibility for your own life and decisions...
I've stated it earlier - there's zero question that the racism of the past will take generations to fix, nor is there any questions that institutional racism still exists today. That said, there are FAR too many examples of black people pulling themselves out of poverty, fighting the racism, and succeeding to conclude that racism is the primary issue here.
If the poor black communities would work to fix reality of 'non-existent' fathers and value education / work ethic instead of continuing to think the 'thug culture' is cool, changes could be made. But as someone who has invested time in the poor black communities I can tell you - white folks and the government can't fix this. The victim mentality that's been sold to so many in these poor communities is powerful and tough to beat - it's nearly impossible to teach someone to accept responsibility when they can blame someone else...
That said, I'll repeat what I said earlier: when a black person has been treated as a lesser person for much of their life, it becomes easy to believe that this white cop shot an innocent, unarmed black kid, regardless as to whether that's what actually happened or not. The world view is just different. And changing that is a monumental task...