The police are people I (we) pay to protect against criminals. When I have to fear police as much as criminals there's a problem, since I'm actually paying the police. Not to mention I'm harrased by law enforcement far more than I've ever been by civilians. Sure we might kill more of our own than the cops (after all we make up a bigger population than cops), but it goes beyond just killings, to how even non-lethal encounters unfold.