The media -- yes, the "liberal" media -- sends the message, and is responsible for spreading it far and wide. It isn't because of some nefarious, overt racist belief though. It's money. Grab 'em with stories of violence and they will watch. It is more profitable to post stories about gang murders and theft and looting and rioting -- which happen, let's face it, but not hourly as the media seems to portray. If you want to steal the 6:00 o'clock news spot, promise stories of rape and violence -- and to find those stories you look at cities, where the people are. You can't rope in viewers by leading with stories of humane acts of kindness. Those you save for the end of the broadcast.
And, of course, the right wing media know the red meat its viewers want to see, to hear and read about, so they gin up stories dealing with blacks, with immigrants -- and occasionally (to make it seem "fair and balanced" -- a deranged whitey.
So, you start out black in this country and you already have a sign on your forehead announcing to whites (esp. police):"Violent prone, dangerous, criminal." And you have to look for an opportunity to disprove that sign. But for chrissakes even if you are a goddamned Harvard professor, the police will still come and handcuff you if they see you attempting to enter your own goddamned house.
Change is coming but it's long overdue and there are a lot of barriers to be knocked down to allow its passage.