I think everybody missed the point with the "goat" and "best rapper alive" references.
It wasn't sarcasm, it was acknowledging that eminem is a great rapper, but he's a bytch/geek/p*ssy otherwise.
MGK had to acknowledge these things anyway since he's already gone public calling eminem an influence/a goat/top 10/etc. in the past. Eminem can't come back with any of that stuff now to use against him in a response.