If someone had a bad experience with different black people multiple times in their country and abroad, would you feel it justified for them to be racist?
What part of your post was about groups who have voluntary vs involuntary membership? Your baseless assertion of "you must become bad to stay police"? Would you look up Eric Talley, who was a family friend of mine, and tell me that he was a bastard or a bad person?
And...maybe people are "born" cops? What if some people are born with ultra high points on "law and order", and they disproportionately become cops through their genetics?