They are taught how to lie in court, how to confiscate property without a trial and how to use intimidation tactics against people that present no threat to anyone. They also have stupid haircuts.
No moral person can remain a cop and not become stressed, since part of their job relies on them enforcing legal, yet immoral edicts.
They can't separate any "goods and services they might provide, from the "bads and disservices" they commit...if they try to, they get fired.
As far as most cops go, they can't go far enough to avoid the inherent contradictions they face. However most cops never face or are even aware of the inherent contradictions, due to their low intelligence, those cops usually have "successful" careers as legal criminals.