Yeah, that's a good point! It's important to consider the truth of the underlying idea, as well as the consequences of how it was expressed—though I don't like that the blog post seems to give up on the latter problem just because it's less objective. Discussions about social values and social consequences are worth having, despite not being subject to pure rationalism.

Still, while both lenses are valid, I'm focusing on the consequences lens, because we're discussing an Atlantic article that tries to invalidate it. It's not misleading to call the memo "anti-diversity", if you're focusing on the memo's role as a social artifact rather than as a dissertation, and that's a valid perspective. Words often serve both roles, and it's important to consider both.

(Incidentally, I don't find the memo's argument to be especially sound, either, so it's not just that it was expressed carelessly—but that's sorta beyond the scope of this thread.)