a head-scratching argument that continually recurs

It runs something like this:

“Object-oriented philosophy claims to push humans out of the center of philosophy. Yet only humans can understand it. Therefore, object-oriented philosophy is a contradiction.”

By the same line of reasoning, you could say that astrophysics claims to talk about distant stars and nebulae, but since only humans do astrophysics, then astrophysics is really just about people.

I have a different view of science, and so should you.

Incidentally, I should also note that if someone says that the speculative realists believe in flat ontology, then that person is all mixed up. Of the original speculative realists, only one (the author of this post) has anything remotely resembling a flat ontology, and even I have explicitly rejected flatness as an obligatory principle (I have two kinds of objects, after all: the real and the sensual).

The flat ontologists in our part of the world include the early Latour, DeLanda, Bryant, and Garcia. In Bonn, Markus Gabriel gave us an early showing of what looks like a bona fide flat ontology as well.

Among the other original speculative realists, Meillassoux would surely have no interest in a flat ontology (when all is said and done, he wants the human to maintain a privileged ontological status) while Brassier is openly hostile to the notion, since the anti-reductionist credo of flat ontologies and Brassier’s eliminativism are simply an impossible mix. (I’m not sure about Grant.)

So, it is simply false to identify speculative realism with flat ontology, and if you identify them then you are not inspiring much confidence in your critical views. It would even be false (though a bit closer to the mark) to identify OOO with flat ontology, since that would efface the differences between all of us on this question.