Really? Thought Em's is a great song. More for the flow than for the disses, but still.
MGK's song was a meme of a diss track. His "your beard is weard" line is my favorite

Guy can't rap to save his life and Em did in fact bury him, just like everybody expected him to.
As for responding - If he's smart, he'll keep his mouth shut, there is no way for him to come back after this, he's simply not good enough of a rapper and will only further embarras himself.
He's prolly gonna milk the situation for Youtube clicks though, and respond - just like Em called it "you’re a fucking mole hill, now Imma make a mountain out of you."