That's the argument he's making. It's not why he's making the argument.

He's making the argument against it because it's not effective in achieving the causes he cares about, and he wants people to be effective. It's all at the bottom of the article:

> I've always been on the side of these things and I've been very happy to see the end to the national conversation in saner and saner ways. But I do not believe for a second that political correctness has hastened those advances, at all.

> And my only problem with politically correctness really, apart from the fact that it's po-faced, sanctimonious, self-righteous occasionally, is that it's not effective.

> I want people to be effective.

> I want, yes, gay people and transgender people and people of all kinds of races and, you know, marginal identities as they may see themselves — I want them to feel comfortable in the world and not hated and not afraid. But I don't think political correctness is the way to achieve that.

It answers the question of why he is arguing against political correctness, which was the question being asked here.