OK, let me make it more clear.
Let's assume two cases:
1. A programmer, his work involves programming (obvious), going to meetings, printing some reports/codes etc.
The biggest problem he can do is introduce bugs in code by mistake (yes, lives can be lost that way), would you expect his peers to tell on him that he was the guy that introduced a bug that killed 300 people in a plane crash?
2. A cop, his job involves preventing crimes, event violent ones, so he sometimes need to use his gun to prevent some of it, and sometimes he has to shoot a criminal.
His mistakes might be killing innocent person. Same thing can happen to his colleagues, so they protect him (just like any sane community would, like your family) - at least unless he turns out to be some sick sociopath.
Do you see relevance now? If you play with code you can just break code, if you play with guns you can break lives.
A side from that I don't get it why there are so many people that trash cops, but don't say a bad word about looters.
Cops protect us from crimes, small and big. They provide order, there are always black sheep, but there are less of those than you think - good guys also make mistakes.
Without a force that provides protection from crimes we would turn into vendetta like justice - have you been to countries that just went out of war? e.g. after the fall of Yugoslavia, there was no police there only tribe and vendetta justice.
Each utopia turns into dystopia sooner or later (CHAZ).