5. The excessive use of "nigga" is incredibly awkward for white people.
White people already have an extremely schizophrenic relationship with rap music, at once fascinated by the form, and outside of it, often an intended audience but rarely acknowledged as such.
Nothing epitomizes this confusion like "the N-word," an epithet that helps mark rap music's territory as, fundamentally, a black American art form. It's a word designed to delineate audiences, to exclude and include, and as such plays with the listener's easy identification with the song's protagonist. None of which means that white kids can't like rap, or that white people can't enjoy it. But the taboo term's ever-present use in hip-hop is a constant reminder of white people's outsider position.
This doesn't mean that whites don't regularly ignore the word's verboten status, but it does mean that their interaction with hip-hop remains particularly fraught.