Eminem cannot be considered the greatest rapper of all time because of his white skin -- at least according to Dr. Umar Johnson ... who claimed as much on Joe Budden's podcast.
The controversial pan-Africanist -- who's mostly famous for his inflammatory online rants and POVs on race, etc. -- was the latest guest to join Joe and co. ... and one segment from their chat is starting to make the rounds in hip-hop circles, 'cause they touched on Slim Shady.
Joe Budden Podcast
Watch ... Umar is making a point about whites that are allowed to partake in Black culture -- including hip-hop -- which he says is a disservice to African-Americans ... and doesn't go both ways. In the same breath, he name-drops Em -- saying he enjoys too much privilege.
Joe asks if he considers Eminem to be one of the greatest MCs regardless of race ... which sets Umar off on a tirade about how Caucasians should never be considered to be the greatest in something that he feels belongs to Black people ... in this case, rap music.