I can warn people every day of my life that cops are thugscum, but my words will usually make no difference to anyone. Only cops can prove me right by their actions. And they do. Daily, in spades.
So why are so many people still in denial? I think it's because they are desperate to have heroes. They want someone to be their protector. They manage to talk themselves into believing that everyone murdered, robbed, kidnapped, and caged by cops somehow deserved it.
They grew up being brainwashed that "The policeman is your friend" and it is hard to shake that programming even in the face of overwhelming, deadly, evidence to the contrary.
Cops have become their own worst enemy- they just haven't realized it yet. And considering that a low IQ (along with a total lack of ethics, and aggressive psychological disorders) is now a requirement for the "job", I doubt they ever will.