It wasn't that complex, but sometimes people just get caught out by even a simple point. Perhaps that day he was guilty of not preparing well, I don't know. Seems harsh to totally discredit him based on being caught out once though, especially considering the huge volume of interviews, debates etc he's been involved in. Overall I think he handles himself very well in those situations, certainly better than most who are out there. That doesn't necessarily make him right or an intellectual though.
I'm not sure where I stand on Peterson, on some issues I think he absolutely knows what he's talking about, but on others he just make huge stretches in logic, the whole lobster debacle being a good example of that. It doesn't help that sometimes he sounds like he is regurgitating a self help book that is on the back of the shelf at poundland.