Because they are poorer in general, because blacks started off as slaves, and emancipation and Jim Crow did little to change that, therefore, black communities are generally poorer than white ones. Police still have no reason to arrest, kill, or otherwise harass black people for things like living in a richer neighbourhood or looking suspiciously at a nearby McDonald's from their car. Whites do it just as much and often more, but its dismissed as just normal stuff. If you think that is justified, I don't even know what to say anymore