That article is typical parroting written by the envious. The arguments made in it are as porous as a colander. Here are a few rebuttals, have fun that writer's nonsense, don't fret over it.
1) Black boxers didn't suddenly disappear, but white boxers from around the world, especially from the east, did suddenly come forward into professional boxing during the last ten years.
2) You know they're desperate when they continue to claim little 5'10" Joe Frazier would dominate the K brothers like an amateur vs. a pro.
3) We all tend to applaud and revere our own, or that which is most like us. Latinos cheer for Latinos and Africans cheer for Africans. But when people of European decent (aka "Whites") cheer for their like they are "racist", which implies they are unlike any other group.