If I'm making the decision based purely on ability, I say keep him. The guy is a top-10 WW.
If I'm making the decision based on whether or not I want to watch any of his fights, I say cut him.
Let's face it. If the former was the only criteria used by the UFC, Okami (and probably Fitch) would still be in the UFC. The fact is, Shields' style makes it literally impossible for him to be involved in an exciting fight (ala Fitch). For that reason alone, gun to my head, I think I'd cut him.
You're not gaining any new fans by showing them a Shields fight. The UFC has to know this.