Ignoring the hindsight=20/20 for a moment, did you have a read on him before the hand started? Because, if not, it looks to me like you overplayed the AJ post-flop, based on the pre-flop action and the call of your bet post-flop. Clearly he's a moron so if you already knew that about him, I think you played it fine except for the basic rule that Musicman posted above.