Apparently Sterling has a history of this sort of thing that is common knowledge amongst NBA insiders. This particular incident seems to be a case of his past no longer allowing him the benefit of the doubt because, like you, I couldn't really tell whether he didn't want her "hanging" with black guys because he was a racist or whether he didn't want her hanging with black guys because he didn't want her to be perceived as the gold digging whore that she obviously is.
No matter though. I don't have the least bit of sympathy for him. "Cuckold" is soooooo freaking accurate!