I don't hate cops a priori, I just don't have any naive fantasies that they're brave heroes who want noting more than to serve and protect me. They're guys collecting a paycheck like anyone else. Some are good, some are bad, most are indifferent and just want to do their job and go home.
However, they have been given an inordinate amount of power, and an ever decreasing amount of personal responsibility. If I shoot someone unjustifiably it will destroy my life (and many times even if the shoot was perfectly justifiable). Cops kill/beat/kidnap/rape on a regular basis and both society in general and the legal system in specific shield them from the consequences of their actions.
Cops are just ordinary people. But they've been elevated to the status of knights in feudal Europe: a special, better class of people who are not truly bound by the laws they claim to enforce. And that's not rhetoric, there are any number of laws that cops or ex-cops are given special exemptions from. And if there's one thing that history has shown it's that power corrupts. And the more power that is given to them as a class, the less accountability that they have as a class, the more heavily armed and armored and aggressive they become, the more they dress and talk and train and act like a military force: the worse that the corruption and abuse of power will become.