LoL how did Pac diss Eminem, Aftermath and Dre? He was dead?
Anyway...I thought about it too, and Tupac was into the spotlight. He would get much more attention beefin with Eminem than he would by collabing with him.
So even though in private Pac might not have anything against Em, in public he'd diss the hell out of him every chance he got, just like he did with BIG.