I appreciate the evaluation, but it's somewhat misdirected. I'm not rejecting humanism, so the presuppositional line you're pushing (that the criticisms of humanism fall back on humanism, after all) doesn't apply.

What I'm doing is critiquing the standard picture to make sense of the hypocrisy of humanists. (The early modern "humanists" defended slavery, for instance, since they defined "personhood" in convenient ways that favoured some humans and condemned others.) Once we see that humanism amounts to a prejudice like anthropocentrism, we find continuity between the ancient and modern prejudices.

And just by way of analysis rather than prescription, we find that an antihumanist must be someone who lacks any such prejudice. The ancient prejudices were narrower (more tribal), in that the modern one privileges humanity and condemns animal species and the mindless wilderness (the raw materials for our civilizational progress).

But that's roughly the analysis I was going for. It's a different way of seeing the landscape, rather than a wholesale defense of antihumanism and rejection of humanism.

Personally, I think there are problems with both humanism and antihumanism, so I'm thinking of ways of combining these things or of overcoming the dichotomy.