"Blacks cannot be racist against whites" does not logically follow from "racism can only come from the oppressor who has the power".
The group in power can be black, as, for example, more or less is the case in the current South Africa, and may be the case in some subcultures (rappers? Basketball players? Some prisons?)
The group in power can be black, as, for example, more or less is the case in the current South Africa, and may be the case in some subcultures (rappers? Basketball players? Some prisons?)