[...] In the case of Eminem, as with Prince, the Beatles, and Elvis, one of the major goals of the movie from the corporate side -- we're talking product here, not art -- is to legitimize the young star in the eyes of outraged adults. From Elvis to Prince, the outrage came due to sex; from Elvis's gyrating hips to the carnal steaminess of Prince's early albums, it was the artists who combined good pop music with appeals to youthful libido that sold the most units (and, thus, drew the attention of moralists).
[...] It's hard to imagine a movie like 8 Mile could be made about a music act like, say, Public Enemy or Rage Against the Machine were they popular enough to warrant a movie. This teaches us something further about the nature of Eminem's notoriety, and that of Prince, the Beatles, Elvis, et al. before him. It's not enough to be notorious or outrageous; you must be notorious or outrageous in such a way as to be useful to people with far more money and power than you have.
[...] Rage or PE couldn't get the 8 Mile treatment if they wanted it (and they probably don't), because their anger tends to be focused at the more powerful, not the less powerful. Fighting the power isn't useful to power; killing fags and hos, on the other hand, works just fine. Pop culture is a tricky balance between validating things people already feel and relate to, and selling, selling, selling.