Police are people. People come in all varieties. There are good people and bad people, smart people and stupid people, nice people and mean people, the list goes on. For the most part they just do their jobs and make our world safer. Occasionally, there's a misunderstanding or a run-in with one of the bad ones, and it leaves a bad taste in a person's mouth. However, these are mostly just the exceptions.
A lot of people have anecdotes about the police and use that as a reason to dislike them. Heck, I've been a suspect in a kidnapping investigation. The kidnapper was seen in the town where I was vacationing at the time and I fit his description. So I had cops hounding me. But you know what? I don't hold it against them, they were just doing their jobs.
Overall, I don't hate the police. People in most of the developed countries have no real objective reason to hate them. Individual police officers who wronged them, yes, but not the police in general.