My question to you is have you ever arrested any other officer you observed breaking the law. If and when police worry their fellow officers will start arresting them is when they will start always following the law.
Have I ever arrested another officer? No. Have I reported bad seeds to the Sheriff's Office (the top law enforcement agency) in my county, since the my now former Chief was covering it up? Yes. Repeatedly. Have other good officers at my department reported the conduct to the District Attorney's Office? Yes.
Did it matter or amount to anything? NO. But it wasn't for lack of trying. As I said in my initial comment, I've seen good officers get shafted and bad ones skate, but I am not one to turn a blind eye to such conduct. The politics are thick on these things, in my opinion, the worst thing is fear of "bad publicity" if such things got known. Thanks for your questions, by the way. This is a particularly bad (for me) but important topic.
Years ago, I remember reading about a Tampa, Florida that broke into a vending machine at the police station. He was promptly arrested by another policeman. That is the one and only time I can recall that happening. I read about them catching other officers driving drunk and letting them go. I read about a detective that, in a fit of rage rammed another driver in the rear with his vehicle, physically assaulted an occupant of the vehicle he rammed, drew his weapon and threatened to kill him [I also seen the video tape of that one].