In any profession that deals in lethal force there are 4 types of people.
1. People who just needed a job. This is the largest category of Soldier, I don't know about Cops.
2. People who are joining the family business. Do what Dad did.
3. People who are idealists and believe their effort makes the world a better place.
4. People who want power over other people, either to bully or kill without consequences.
The first three types are pretty harmless, they want to go about their business and do their job. The fourth type is dangerous as they have a need to interact with people from a position of power. These people cause the vast majority of negative PR for the Army and Police departments.
But these sociopaths are protected as long as they can keep the loyalty of the other three types. Ever wonder why so many "internal investigations" clear an officer of all charges and return him to duty? It is because the "thin blue line" closes ranks and protects their own, because everyone else feels that maybe next time they'll need that protection.
And that is wrong. In the Army we have the same problems keeping all the bad apples from ending up in the same basket, and good leaders are always looking at HOW their Soldiers do their jobs, not just the results.
But we have to break apart those that close ranks, and remove the bad apples. Because if we don't then we lose authority and people actively resist us. The criminal who killed 4 police officers in Oakland was hailed as a hero of the people by some. The Oakland Police Department does not have the support of the people because of the 4th type of cop. I don't need to remind anyone what the effect of Mai Lai or Abu Gharaib was on the reputation of the US military.
So watch out for the 4th types, and show them no loyalty because they will destroy your organization if you don't get rid of them.