There was that one cop in...cali? That started actually hunting other cops when he realized shit was bad. He didn't change anything, but he might be the only good cop.
No idea, maybe. The extent of my knowledge is a half remember weird news segment on a radio show. I do remember he got the other pigs do riled up they'd attack random people (more often).
It's just the default stance. Kind of like assuming everyone on the road is a bad driver and driving defensively as a result. It's safer to assume every cop you interact with is actively looking for a way to screw you over, will lie to you and will violate your rights given the opportunity. Even if it's just most, or hell even rare that cops are bastards it only takes one interaction with one to have life altering consequences.
That way you can defend your rights and be pleasantly surprised on the rare opportunity you encounter one who isn't a bastard, rather than be constantly disappointed (and possibly in jail or dead).
I'm living in a world that by default assumes all military and police are good. I've slowly over time seen enough to migrate to the other side. Fuck them all. And especially fuck the cult-like worship of military, and to a lesser extent, all policing.
The grey area you're referencing also leads to bipartisan demands. Look where that gets us with extremists? No thanks.
Statistically speaking, any cop I see or encounter is likely some kind of piece of shit, abusing their spouses, or their kids, or other people's kids, or generally being bigoted in their job and likely seeking excuses to overly apply authority put of their subconscious need to control others and feel important, or just enabling other cops to be assholes. Fuck em all.
It's actually hard to become a policeman here. First you have to pass some tests to even get accepted to police school, then you have the basic training consisting of 19 months theoretical and 5 months practical training. Only after passing all the tests there, you can start as a low level policeman, requiring both more training and experience to progress.
Random people who just want to get into a position of power don't pass.