There are plenty of skilled, athletic white dudes that can hoop it up, who are just regular ass dudes. That's what Billy is.

The whole hook of the film is that he puts that goofy white guy caricature on as a mask, as part of his hustle.

The fact that cats like Eddie and Richard made fun of a caricature for so long doesn't really make a difference. They made fun of a caricature, and that caricature is a costume Billy puts on as a hustle.