Wouldn't say they're evil necessarily. I believe they have a warped sense of justice and morality, certainly, but not evil. Well, not most of them at least, but evil people would certainly gravitate towards a position with the power and social status that comes with being a cop.
Would I say the majority of them are dirty, power hungry try hards? Most certainly, but I'm on good terms with a lot of cops. One actually let me out of the car for a little bit while he was taking me to county so we could smoke a cigarette. Granted, I was in cuffs the entire time, but it was nice of him and he actually could've gotten in trouble for it.
I've also had an officer pull their gun on me multiple times, most of which were unnecessary. First time I was 14 years old, and his partner got hit by a car chasing my buddy when he ran off. He kicked my other friend's leg out from him and slammed him into the pavement when he said he didn't consent to a search, then bragged about piledriving him (again, he kicked his leg out from under him) after the fact.
My friend was only 12 years old at the time.
So yeah, some cops can be cool, and others can be awful, but most of them are just dicks with control issues.