The key point for me here is that Peterson's a scientistic dilettante. Like lots of others who have some scientific training, he condescends to the humanities. The sciences are like New York: if you can make it there, you can make it anywhere. So Peterson pontificates on religion, philosophy, history, and so on, and he does so sloppily and fallaciously because he's just slumming due to his patronizing arrogance.

Scientism here isn't a theory, but an attitude. The scientismist dismisses the nonsciences in a condescending way. Peterson dismisses them not by saying the humanities should be eliminated. Instead, he dismisses them by presupposing that they deserve to be practiced only poorly (because they're not as sophisticated and rigorous as the sciences).