On watching it again (now that I'm not at the office) I think it's about as racist as Goldie-Looking Chain to be honest... that is to say that it's the hip-hop style (or the style of hip-hop) rather than "black people" that's the butt of the joke here. I've seen how easily some people don't make that distinction though, I know I've been uncomfortable where I know what's really in the mind of the er... 'joker'.
I can only speak for myself of course but sometimes it strikes me that the racism can sometimes be more in the accusation of racism in reaction to a thing rather than the thing being reacted to as racist. On more than one occasion it's almost as if the mere reference to 'black culture' by someone who isn't black is verboten... like we're not supposed to be referenced or looked at or considered as part of the general culture, black as untouchable if you see what I mean... probably not because I'm probably describing what I mean wrong. "Don't look at them, don't use their music, they are over there and not part of the general body of work called human life". Perhaps when the concept of cultural-appropriation effectively becomes a form of cultural segregation, or racism in negative space ("if you're born a white man then you have won in the lottery of life", which is somehow mysteriously different from Kiplins thoughts on being born English, but said as if guilty rather than proud- it's the same essential bullshit world view surely?
Anyway not to drift off into wherever I'll just say that if none of that makes any sense at all then I blame the after-work red.