There's a saying. If you want to learn a man's true character, give him power. I've found that the percentage of people who will misuse it is relatively small. However, there's a very strong correlation between the people who want power and those who misuse it. Being a police officer gives a person power. "Some" of the people who want to become cops want to carry firearms, for ex. Otoh, the majority want to be cops because they're seen as heroic (because of the good deeds they do). But, being a hero means taking risks, and not everyone wants that. So, yeah, certain types of people will be attracted to becoming police officers.
Anyway, the realistic way of looking at police is as "civil servants" with particular responsibilities. I agree, they must follow the law, and when they don't, they should be punished more severely than ordinary citizens. It's true that there's a bunch of corruption, and that cops are reluctant to expose their colleagues. Hey, that's completely understandable, too. It's human nature, and probably a good idea if one wants to stay healthy in that profession. When I worked construction, other people often had my life in their hands. So, the saying was "It's nice to be nice."
But, don't think that I'm just blindly defending the cops. I've seen police brutality up close. Otoh, I've had cops help me out --in Boston, no less. Hmm, most of the complaints about "the police" in general were about how frequently young black men were getting shot (in their homes, on the street, in police cars, etc), often in the back or by mistake or "thought was holding a weapon." Well, it wasn't just the shooting; it was the almost invariable decision that it was justified. For ex., this happened last year: "Police claim handcuffed prisoner, in back seat of squad car, shoots self in head"
http://www.examiner.com/article/police- ... -self-headNow, how someone, iinm, with his hands handcuffed behind him (in a car, after being searched) manages to shoot himself in the head, I don't know. But, to me, the fact that it is offered as an explanation means that there's a possibility that it'll work.
I also think that police departments have cultures specific to where they are located. Some things will go on is one precinct that would never happen in the adjoining precinct: drug sales on the street, for ex. Some people are more likely to get beaten up in the station holding cell or even before they get to the station. And, it's not strictly a racial thing.
"A man is rich when he has time and freewill. How he chooses to invest both will determine the return on his investment."