Are police really responsible for most violence (murders / robberies etc) in the US. If so it would seem better supervision would lead to a huge reduction in those crimes.
If you believe the news headlines without thinking about how they're feeding you a carefully-constructed narrative, then yes. The stat everyone likes to quote is that cops commit some ludicrously large proportion of all murders by strangers, but of course people don't generally go around killing people they don't know. Beating, mugging, burglarizing at gunpoint? Sure, there's plenty of that... but murders are generally someone known to the victim.