Ancap here. This is just what happens when there is an unaccountable violent monopoly provider of security services. It's exasperated because the provider of security services is also the monopoly provider of justice. So what we end up with is abuse. Want to stop this? Break up the monopoly and allow free and open competition in security and justice services.
I came to say this, though I am not a leo.
Fortunately the age of modern media and internet is allowing all to observe and a bit more transparency to take place with the law enforcement. It's no surprise they are already trying to shut that down in several states..