Good point. But to take it even further, I doubt that he HAS any followers.
He has fans, of course, but I don't think for a moment that his lyrics are a threat to the President. He's not a left winger, he's a nihilist.
Of course, it's also important to realize that the doesn't have the same fan base as the Dixie Chicks. It was predictable that there would be a reaction from their basically conservative Country-Western base. Not so from the alienated, apolitical young people who listen to Eminem.
To them he's not being political, he's just being "edgy". And as OpusatFR points out, they don't vote anyway.
Sure they do...they just don't know it. And they always vote for the guy with the big "D" on the ticket...