As much as I agree that he seems pretty far "out there" sometimes, I'd say that his argument that Guns'n'Roses still exists and that it would be illoyal for him to play with the former members under the same name, holds some water.
I don't know if that's his real motivation, but I can see how the "new cast" would be appreciative of him taking a stance and saying "you guys quit, this is my band now".
Good. He's insane. I always thought GnR was a great rock band ruined by a whining, sniveling, lady-boy of a lead singer. Induct the other guys on their own merit. They deserve it.