Until the “good” ones do everything in their power to get the bad ones off the force, they deserve to be painted with the same brush.
Cop, soldier, politician, lawyer, teacher, pastor, I don’t care, you deserve to be judged by the worst behavior you tolerate in a peer. Everybody on the other side of the ‘blue line’ is responsible and no better than the worst cop they don’t do everything in their power to get off the force.
Bad cops are like bad lawyers - they know exactly what they have to say so that they cannot be proven to be in the wrong. Many good cops are, no doubt, suspicious when a cop shoots a Golden Retriever puppy, but it's hard to prove a crime when the "dangerous" dog is dead, and the only statement comes from the shooter. They are limited in their ability to prosecute criminals without evidence but figure they will catch the crook (whether in gang colors or wearing blue) eventually, and they have to tolerate that situation because there is no lawful alternative.