To me it's really about what Jay-Z said before on the radio when he said "No one is scared of 50 Cent".

He made it clear that he was not afraid of 50 CENT instead of just sayin' he wasn't afraid of ANYBODY, so now Fif is pushing him around to see his response.

The way I see things now is that Jay-Z has no choice but to respond, or it will be clear that he is actually a punk avoiding any kind of competition.