In general, I support them. However.
Giving people power is always a dangerous thing. If you don't supervise them closely and grant them a certain degree of anonymity, things can get ugly quickly.
Some months ago, there was a demonstration in Berlin, Germany (and they're going to do it again), themed "Freedom, not Fear" and was against the government's plans on increasing surveillance. As such, they picked a route that was tightly packed with surveillance cameras. At some point, a policeman got aggressive (I wasn't there, but it's the story that's generally believed) and started to bring fists into a verbal discussions. In the ruckus, policemen coming to his aid also ran over a wheelchair user and they didn't even think about turning around or apologizing after the whole incident.
The reason I brought up where and why the demonstration was held is that - ironically - not a single surveillance camera recorded the thing. If it wasn't for a low-quality cellphone video on YouTube, the policeman would have gotten away with it as none of his colleagues would tell his name and policemen don't have a number on their chest or something to be identified with.
That said, I don't think the police is entirely "bad" or entirely "good". Although I don't have any statistics or something, the good person inside me wants to believe the "bad apples" are just exceptions and the big majority of the police is capable of dealing responsibly with their power. You can make very different experiences with policemen, but mostly you only get in contact with a policeman on duty if you did something wrong, hence many people that get first-hand experiences at all probably don't have much love for the police.
Like I said, I generally think of the police as "those who protect us", but if they're not held on a leash tight enough, they become "those we need to be protected from". Then again this is true about anyone with power over other people. And now I'm running in circles and cut the comment, hope my opinion was pleasant to read and affected your mindset.