Philly has had a long history of racism from the riots in the Civil War era through the 60's (when I lived there) and beyond. When I lived there, Chief of Police Frank Rizzo (later elected mayor), among otherf things, threatened people with gunning them down in the streets using an armorplated school bus with machine gun ports in the sides. This was in response to the killing of MLK when Rizzo declared that gatherings of more than a few people (and we all knew what neighborhoods he was talking to/about) would be his target, regardless of their actual behavior.