And why are people always looking for reasons to hate cops?

Because they're the most visible branch of the government, in charge of stopping people from doing shit they shouldn't be doing. They ticket you, they shut down your raucous parties, etc. People hate cops for the same reason they hated their parents as teenagers.

Is it the media's fault that they get away with murder?

No, but it is the media's fault for showcasing the ones that do, causing people to vilify cops, causing cops to not trust the citizenry, leading to more violence from both sides, it just so happens that one side is better equipped for it. The problem isn't cops, the problem is the citizenry and the cops not getting along or trusting each other, because the media paints the cops as villains by only ever showcasing the worst of them.