Another option, which I think is the thing that makes more sense, is this fact that the police are a reflection of the occupation of certain neighborhoods and certain parts of cities that are designed, basically, to keep the bottom down and basically maintain the status quo, but out of sight, so that the other side - the people in power, the people with money, the people with comfort, the people that are living in the "safer" areas - are sure that they can sleep safely in their bed while bad thing are happening to people and it's not their problem.
