The gaping great highway that can be driven though that argument is that he actually has turned out to be right.
What argument? Why didn't he leave before then? Surely the idea was to get a well supported team, who was playing well, were solvent and playing in a great stadium, up to the next level. Nobody is deluded enough not to know that Sunderland aren't a bigger club. Let's see how well he does. Brighton are going through a sticky patch so if you want to desert them go ahead. Somehow I think you'll be back when things improve.