Because the police are mercenaries, not wild animals. They generally don’t bite the hand that feeds. Besides, they still have 99% of the population to target.

Because America worships pedophilia and psychopathy.

Why don’t the king’s guards attack the king?

The police know their job is to enforce the law, but they also know who gets a free pass… or at least who gets a lot more leeway than other people. At a minimum it changes “shoot first and ask questions later” into “ask questions then maybe shoot”.