I don't think that every instance presented by BLM is necessarily police brutality. But some are. And BLM are not the only people saying this; scientists, researchers, academics, lawyers, and people in contact with the criminal justice system do confirm that racism is real, prevalent, and systemic. You absolutely have to accept that racial injustice is real, violent, and prevalent, police corruption and violence is real, violent, and prevalent before we can continue, or there is really nothing to say.