Most aren't. Most are just doing their job. I have found, as long as you are respectful and reasonable, they will return the favor. I have run into a few young cops who are on the force to get back at those who picked on them in life. Those guys are hard to deal with.
I was pulled over after having just passed a 18 wheeler, I was doing about 80 in a 65, but I was slowing down [after having JUST passed the truck]. He pulled me over, and I was polite, stating that I was passing the truck because it was kicking out rocks, one of which hit my windshield. He yelled at me saying he didn't want to hear my excuses, and proceeded to tell me I was lucky he wasn't throwing me in jail for endangering others. Prick. It was 6am on a fucking Saturday on the I-90, a 4 land highway, with about 4 cars on the road at the time. But in the end, I was still polite.