The principal contradiction in OOO is not that of the posited impossible relation between subject and object. It is squarely in their account of « objects », in the distinction between real objects and sensual objects. No example of a real object can ever be given, or even « alluded » to. All examples are illusory, the opposite of what people think to find in OOO.
Harman tries to get round this impossibility by means of his doctrine of « allusion », but this is to confuse « reference » and « allusion », two quite different things. All referential sciences are condemned by Harman as undermining or overmining. He pretends that « allusion » remains, but even such a tenuous signifying relation is inconsistent with the principle of withdrawal, i.e. of withdrawal from relations (to use the full title).
These contradictions and confusions are fomented by OOO, but it can only get started by ignoring them and making its audience forget, or never even notice, their existence.
In the case of his critique of Zizek’s supposed subjectivism, what Harman ignores is that Zizek has noticed these sorts of contradictions, and that Zizek’s basic step is transposing the subject-real (and not « object ») parallax into the real itself. This step is the opposite of subjectivism, and Harman misses, or travesties knowingly, this primary point (Theorems I and II in SEX AND THE FAILED ABSOLUTE).
Note: I am grateful to a discussion with Jack Black for helping me to clarify my ideas on this subject.