To most people these communities are the epitome of irrationality. Not only are they rioting and destroying their own neighborhoods, but they are also doing it for unjustified reasons seeing as how most of these incidents turn out to be the legal and justified use of police force.
I don't understand why the black community keeps doing this. They are making themselves look terrible and losing support of wider society. Why were the civil rights protests effective--they were both non-violent and justified. The US was 75%+ white during the civil rights era and to enact change civil rights leaders like MLK Jr. understood that they needed to convince a majority of white people that the discrimination against minorities was immoral and they succeeded because they were clear in their obvious grievances and non-violent. Violence, even justified violence, is looked down upon as a means to force societal change in a democratic state and unjustified violence is especially frowned upon.
While the US has had large demographic changes since then, the black community is still a minority and needs to convince the wider society that their problems either economically or with police need to be addressed and they are doing a terrible job convincing with this type of behavior.