Homosexuality is generally still frowned upon in the American black community, particularly among those with any kind of association with the black church. Additionally I think most Christian black leaders - even liberal ones - bristle at the idea that behavior-based discrimination (LGBT) is the same as race-based discrimination. So even if leftist blacks say LGBT discrimination is evil, I don't think most would equate it to the suffering that blacks went through years ago.
Add to that the machismo that goes with being a young, black male athlete and you have a less-than-accepting environment for a homosexual male.
Of course I'm sure Mr. Wilbon needs a reason to bash conservative Christians, so he chooses to blame it all on that.