Most popular cop shows running now (like Law and Order) are pure fantasy, propaganda, and wishful thinking. They're made to present a much better version of reality because the real story would turn people's stomachs and lead to a level of unrest and distrust that would help no one in the short term, least of all the police.
And trying to make a show highlighting the dark side of policing would be close to impossible these days. Movie shooting relies a lot on the police for things like crowd and traffic control, and even for using real cops and equipment in some scenes. The police can make it very hard to continue effectively. It's the same story as with the Pentagon and military themed movies [0][1].