Howard, who was later Oscar-nominated for Hustle & Flow, has stated that he confronted the veteran comic after his scenes were cut from a 1988 episode of The Cosby Show.
Howard said Cosby had him blacklisted in the entertainment industry following the confrontation.
Cosby told EURweb: "I don't like something being out there that I know for sure isn't true. There's no person that I know of that I've ever felt strongly enough to call and say, 'If this guy calls, don't book him again'.
"Somewhere, there's something missing. And that is somebody saying either I never said those things, or, I'm sorry. And it's taking too long. And these blogs go out, man. I don't want people looking at Bill Cosby talking about, 'I had people barred'. It just gets too far out."