Good cops get chased out.

Good cops who stay end up getting silenced or killed.

Until you cut the rot, ACAB.

"A rotten apple quickly infects its neighbor", the 1130s version of the famous proverb.

It also suggests the solution: remove the bad apples before they can spoil the bunch. But, bad cops are protected, and as a result the whole institution is rotten.

Also, if you end up with a whole box full of rotten apples, the only solution is to throw it away and start fresh. Police reform processes almost never do that. They try to keep most of the cops, even the supervisors, in their jobs. Then try to fix it with extra training, or outside supervision or something.

There should be laws, and if there are laws there's a need for law enforcement. But, other countries around the world have managed to do that in a way where their law enforcers are properly supervised. They've found a way to have specialized units that deal with violent crime or organized crime, so that the rest of the law enforcers don't have to walk around with a life-or-death mindset. Most importantly, they have a culture that a police officer is a public servant whose main job is to help people in very stressful situations. In the US the culture is that every person you encounter is potentially going to kill you, so you and your brothers need to approach every situation as though your life is on the line.

Good cops don't let bad cops do bad things. Which is another way of saying that I agree with you, but I would prefer to categorize cops based on their actions and not based on their theoretical potential, because we have to live with the former. Or die from it, as happens all too often.