Maybe because Kamau Kambon doesn't have a 4 hour radio show?

It seems that at least the organizers of the forum where Kambon made the remarks did denounce him.

"I organized the Pro-Black Media Forum where Dr. Kamau Kambon made the comments about exterminating all whites while on CSPAN," Opio Sokoni explained to WND. "No one could have ever known that this former North Carolina State University professor would go off the cuff and make such immoral and unproductive remarks. We were all taken off guard – especially since he had said earlier that black people were not niggers but imitation niggers. If this is the case, his comments were not pro-black but imitation Hitler."

WorldNetDaily: 'Exterminate white people' ripped as black hate speech