I've only ever talked to police officers twice and they seemed nice. I have heard bad stories about them, though. About their behaviour in my country and in the US.
Apparently it is allowed here for police officers to go undercover during a legal protest and to provoke fights, so that they have an excuse to arrest people. That really disgusts me.
However, things like people getting killed by the police are very rare in the Netherlands, thankfully. Whenever a policeman uses his gun for a warning shot, it already makes the news. And when they have to shoot a suspect, they aim for the leg.
It does scare me a little that they are allowed to do certain things, but I am never afraid that one of them will seriously hurt me.