It's all a bit stupid really, isn't it? I thought the same thing myself in the midst of the promo.
If Cena remains fired, he will keep attacking Nexus.
If Cena is re-hired, he will stop attacking Nexus, yet he will just attack Wade Barrett on his own instead. Where the fuck is the logic in it? He may as well have just said "So Wade, what I'm basically saying is: re-hire me, so Nexus can split up and then you and I can have a feud... because Miz is feuding with Orton and I have nobody else to play with."
He has no reason to "stop" attacking Nexus, and furthermore... Nexus have no reason to trust Cena or believe that he will stop attacking them, either. They are still all enemies here, regardless of Nexus starting to resent Wade.
I hate how they have to be so fearful of Cena when they are a group of strong men themselves. He is made out to be some collosus mastodon superbeast who will always be anywhere the Nexus are, 24/7, ready to ATTACK!!!11... regardless of him being "fired" now and just a "fan in the audience". It's totally overlooking the fact that security guards exist and the fact that some muscular man in a bright purple t-shirt is hard to miss.
It's all a fucking joke of a storyline, but I suppose I should be used to the WWE not making sense by now.