A riot is the voice of the unheard. You're looking for rationality among the oppressed in the face of the irrationality of the oppressor. Why do the oppressed have the obligation to be somehow more rational? Why is it any less logical to destroy an area in which you live (and to be honest, a CVS in Baltimore and a convenience store in Ferguson aren't really the high water mark of community pillars) but why is it less logical to destroy those places than to allow cops to kill black people and get away with it? You're asking the wrong questions I think. More importantly, and this is a bit more daring, but the uprisings should be condoned because violent uprising is the only route to actual changes. The feds came into Ferguson and Baltimore for oversight of police actions after the uprisings. The Civil Rights Act didn't get signed because of people sitting in neat little rows making clever arguments and begging for power to be given to them. It may be an uncomfortable truth, but power isn't given willingly to the oppressed.
I try to approach situations through the path of logic and reason. That's just how my brain works and it's hard for me to see a different view. All of this is an attempt at doing that. In my mind, I would see the oppressed taking a more rational approach than the oppressor as an extra mark in favor of the oppressed. They're having to live through unreasonable conditions born out of hate and yet they rise above it in spectacular fashion, refusing to bend to the call of violence. However, I do understand that this approach wouldn't garner as much media attention. Unfortunately, the media only cares about how much stuff got blown up because ratings, so I can understand how resorting to violence may the the only option to get your cause onto the national stage. Not everyone who fought for civil rights in the 50s and 60s used violence to achieve their goals. I can't imagine that the violent protesters would have succeeded without those refusing to take part in violent acts. Maybe nonviolence wouldn't have been a success either. I don't truly know enough about all of it to make a solid statement. What are the right questions?