Not in the sense of any retardation. I think he's just a private person who's not comfortable on stage, and he deals with it by basically shutting down. You get the feeling that there's some complicated dynamic for why he's up in the first place, since he seems so unhappy to be there.
I've seen several people grow and become more comfortable onstage at this open mike, which I want to write about later. Maybe eventually it'll work for Bentley, too. I hope so.