Because the establishment via entertainment industry, social media, and various mega corps are financing and enabling this behaviour based on a skewed understanding of police brutality. Most of the useful idiots supporting this narrative claim to be the underdogs while turning a blind eye to the working class victims suffering from this nonsense.

Are there corrupt police? Sure, but the fact of the matter is the numbers/data don't support this media hype narrative of the police getting out of hand and committing genocide on blacks. Only about 300 black people die a year by the hands of police, non white cops are more likely to kill blacks, cops are 18 times more likely to be killed than black criminals, and adjusted for proportion blacks are more likely to commit crimes which is why they clash with the police so often.