I think he gets postmodernism wrong and frankly, so do a lot of postmodernists. I see postmodernism as "Defense Against the Dark Arts". The postmodernist's tool kit -- the silly word games, denial of reality, and so forth -- are all borrowed from the right, and from capitalist society (in particular advertising and PR). And they play silly word games, talk in circles, and deny reality because they're preparing their students for a world in which the enemy have made that the norm for discourse. So when the postmodernist says "there is no reality" what they're really saying is the reality you know, and the rules for perceiving and inferring that reality, have been compromised. When Foucault says there's really no such thing as science, what he means is that science itself has been compromised, and you can't use science against the enemy because the enemy already controls it and will turn around and use it against you.

But I like Peterson's style -- bombastic without being antagonistic, and highly principled -- and about the psychology bits he has some really interesting things to say.