If the whole thing wasn't staged, it was a real weak reaction from Eminem. I mean, it was a joke, (even if it seemed that it went a little too far.) But if you look at things, which Em already pulled off, it wasn't that bad at all.
I just expected a more funny answer from Eminem. Instead of leaving the audience, I would've propably said something like : "Hey if you already have your head between my legs, you could at least clean my balls!" (or something like that.