There are bad cops, and they often are not held accountable until something really bad happens. That said, by far the vast majority of police officers are good. There is no systemic police terror here. Compare and contract to most Third World nations where the cops are just a state funded criminal enterprise.
These idiots are, well, clueless idiots.
The first time some pyscho rookie beat up a prisoner, he had done 20 years for a felony under color of law, the rest of the department would either take it as a lesson learned, or quit.