Not all professional groups have ironclad unions and official rules that prohibit their victims from even knowing the result of the investigation. And most of them aren't allowed to shoot innocent people [1] or beat them to death [2] and suffer no consequences. It's one thing if you let the colleague slide on a minor infraction, it's another think when murder becomes minor infraction. That corrupts. One can not see people around you literally getting away with murder and not have consequences for your morality.

[1] http://jonathanturley.org/2014/02/12/eight-police-officers-f...

[2] http://blogs.ocweekly.com/navelgazing/2013/12/kelly_thomas_f...