Corny punchlines don't bother me. I actually enjoy them. It brings an element of humor in the music. It actually takes some creativity to come up with that shit. J. Cole and Jay-Z say a lot of corny shit and don't get chastised for it but if it were Cam'ron or Wayne people make a big deal about it.
Ah c'mon nigga that's weak. If he were writin' shitty punchlines on purpose in an ironic way, like to satirise the current state of hip-hop or something, then I'd say 'fair enough'. But he's not doin' that. His lines are wack coz he is wack