Oh, come on. I've only had sex with one horse, and it was a small and very manageable (and super cute to boot!) colt, and that was years ago. We did some pretty cool tricky stuff and then he rode me bareback for a while. I don't regret a moment of it so fuck off. And it was years ago, anyway.
I can't speak for Eminem, but I get the feeling he's not a horse cock kind of guy.