I have a bit of a theory about cops and why some are asshole and some aren't.
The problem I belive comes from too many cops in small towns, (at least part of the problem anyway) I come from a pretty small town and this is a real problem.
I have since moved but I lived there for like 13-14 years and never once got helped by a cop. My house was robbed once and they couldn't help me get my stuff back (not necissarily their fault I know) but almost every time I was pulled over or me and my friends got busted somewhere the cops tried to get us for everything they could.
The deal is that if you live in a small town the cop busting you may well have been in school with you, or at least he/she remembers you from a previous encounter. On top of that there are probably too many cops in town than there needs to be. In the town I'm from you never got pulled over by just one cop it was always at least two and sometimes up to four, they just have nothing else to do. Being bored can agrevate a person so my theory is that bored cops in small towns give the rest a bad name. At least partially anyway, I'm sure there are plenty of good cops out there who just want to make the streets safer, and plenty who, for the most part, want to use their authority to harass people who piss them off.
I guess cops are just like everyone else some are nice some are assholes, but most are somewhere in between.