I'm one of the biggest supporters of W that you'll find, and I don't see anything wrong with those lyrics on their face. Yes, Free Speech does give you the right to yell "Fire" in a theater, but it also means you'll have to deal with the consequences.
Speculation here:
Eminem might have known this would cause a big stink. BUT, the people that are all up in arms about it weren't going to buy his album anyway. I wouldn't have known that he was coming out with a new album until I heard this, and I'm sure a lot of people are like me.
In short, relax people. It's just words. He didn't make an attempt on the President's life. Em knows his audience. They won't be too upset about this. On the other hand, The Dixie Chicks apparently didn't know their audience and made a big mistake, though they've come out of it O.K.