” What we are saying is that a system EXISTS wherein a black people are disproportionately treated in racist ways.”
The people who are “disproportionately treated in racist ways”, is being black their only commonality? Is that the primary factor for what you determine to be mistreatment?
From my perspective you are pointing at your conclusion as proof of your hypothesis. We see this as racist, therefore racism must be the cause of what we see.
THAT is why I am skeptical of sociology, rhetoric and cultural studies.