There have been a lot of stories recently about police abuses of power. Undoubtedly, these stories are not representative. The vast majority of police-civilian interactions do not end with death or violence. Most cops are good cops.
But that doesn't matter, when the whole system is bad.
When a police officer can kill someone with no provocation, on camera, and get away with it, it doesn't matter that there are more good cops than bad cops, because the good cops are part of a system that does nothing to stop the bad cops.
And it's not just the major abuses like that. I've heard (not being a cop, I don't know for sure) that police officers will usually not give other officers tickets for traffic violations. Of course, that's a very minor thing, but it's indicative of the problem. Police officers are held to a lower standard of conduct than civilians.
"With great power comes great responsibility." Unless you're a cop.