I love Token!!!!! And that was such a great episode.
As others said, it has to do with the "black people have rhythm and white people can't dance" stereotypes.
This is a culturally-specific stereotype limited to the United States. It's not that white people are biologically inhibited rhythmically, or that black people are biologically capable of dancing . . . it's part of African-American culture and the slavery experience. Slave spirituals, soul music, hip hop, and all that jazz promoted movement and rhythm and polyphony and community. North American colonizers and slave-owners, however, were largely Protestant who are notorious prudes who outlaw dancing and fun in general :-)
How's that for a stereotype ;-)
But seriously, if you look at music videos from places like France and Brazil, black people don't dance anything like they do in mainstream American culture.