I make specific assumptions to demonstrate one example. This is a common technique to show problems with data.
My point is not that the people are biased against rappers, and that leads to a higher conviction of blacks. My point is that if they were it could lead to biases in the data.
As for racial profiling itself it has been used for a long time. It is effective at catching people of certain races.
On what basis do you assume police have an equal chance of catching a culprit regardless of their race/background? To me that seems a massive unsupported assumption that you need to conclude that the arrest/conviction data reflect the crimes committed data.