> These are not "decent people".

I really don't think it's that clear cut. The cops who turned their backs aren't all, necessarily, bad people. The insularity of police culture generates significant peer pressure for cops to cover each other's backs and to protect their mutual perceived safety and self interest.

They respond to perceived attacks on interests in a similar way to what many subcultures do when they feel their interests are being encroached upon; they protest and grow more insular in solidarity.

This tends to lead to a bubble and allows otherwise decent people to, inadvertently or otherwise, overlook the shortcomings of "a few bad apples", in the interest of protecting people who they think have their best interests at heart.

I'm not saying this is good, it's just important to remember that cops are humans and behave like humans. Training is supposed to reduce the incidence of human misbehavior but I think that even just the fact that police wear uniforms tends to make them take the side of the "team" that they're representing.