I think "corruption" comes from the idea of leaven leavening bread, one rotten apple spoiling the bunch. It is so important that corruption is dealt with.
Many in public offices, police, teachers, politicians, priests, judiciary... need to stay good and squeeze out the bad... the next danger is that we will lose trust in all authorities.
On a different angle, I once heard from a very good source about a well known "news" presenter who was good at pointing fingers, but if people knew about his past they might also see that hypocrites can point the finger at hypocrites.
Getting back to the police, I feel sure that most are of good character, however we are all human and make mistakes. I'm not talking about people that deliberately, wilfully, cunningly, continually, purposely commit bad acts.