I think it's very easy for a position with power, such as a police officer, to become corrupt. I don't think all police officers are corrupt, but I think as a profession, they operate in a type of brotherhood that perpetuates corruption and abuse of power situations and should be scrutinized more by the judicial branch of government.
The police are often granted more leeway to do whatever they want: they get off scot-free when they kill unarmed civilians, and they are now allowed to use illegally obtained evidence in the courtroom. This breeds corruption and means that we can no longer safely rely on the police to do what's right.
No, I do not think that the police are corrupt because it seems that the actions of a few dirty cops taints the image of all police officers. I think that most police officers are good, honest people, but there is a small minority of police officers that are corrupt.
To make a broad statement the police are corrupt is, in my opinion, not even possible. Has anything corrupt ever happened in connection with the police? Sure, probably but as a general rule the police are doing exactly as they are meant to which is keeping the public safe and law-abiding.