Why are musical artists always assumed to endorse every topic that's in their music.
TV executives, movie directors and producers, and authors can all make works about truly horrific things and nobody believes they personally endorse them.
Bobby Darrin could sing about knifing a guy with blood all over the place and then sinking him in a river with a cement bag and nobody thought it was anything but just a song.
(P.S. Don't really care for Eminem's music... like Bobby Darrin's better. But I agree with your point.)