That's because it is. BLM are social activist, not law enforcement. They hold police accountable because they have legitimate, legal authority to kill, and oftentimes face no consequences when they do so.
To make it simple: Ray Ray shoots and kills a little girl. He gets arrested or becomes a fugitive of the law. He is ostracized from normal black society. The only people supporting him are other POS criminals and gang members. In that situation, who does BLM protest? They go to the jail and protest once Ray Ray is arrested, or go to his hood and protest? I don't think the latter will turn out well when dealing with POS who just killed a little girl and has nothing to lose.
Now, cop kills unarmed black man under suspicious circumstances. Cop gets paid leave, qualified immunity, no charges filed, and can continue to live his best life as if nothing happened...that is until there are protests that put pressure on police departments and DA offices to take action. Me personally, I hold police officers to a higher standard than POS gang members.
Side bar. It's always the black community that must be held responsible because of what one black person did. Why do I, living in Virginia, have to feel personally responsible for what some POS gang member in Chicago did? Is it the black communities fault for what the NY subway shooter did? Should we be protesting him outside of his jail cell? White person commits a hideous murder, he's a bad INDIVIDUAL. But a black person commits a hideous murder, BLACKS HAVE TO DO BETTER.
Now I do 100% agree that all of this starts at home, and people need to raise their kids better.