That's the problem: a lot of cops aren't upstanding citizens fighting the evil of the world. They're normal people who make the same stupid mistakes us non-cops do and they have bad days like everyone else. On the whole, most street cops are high school graduates at best and many of them have authority issues (as in, they like to exert theirs). The smarter ones move on to be detectives. Cops are also mostly good people, but that job also has a tendency to attract more scoundrels than a normal non-authoritative job due to the power it involves. It also doesn't take much to become a police officer.