Moral error theorists often respond to the epistemic companions in guilt strategy by adopting the Disparity Response: reject the putative parity between moral and epistemic reasons and claim that though the former are irreducibly normative, the latter aren’t. I argue such a response fails. Expanding on Das’ Australas J Philos 95:58–69, work I present a master argument against Disparity Responses: the arguments moral error theorists use to advance their conceptual claim apply in the epistemic domain also. This prohibits the error (...) theorist from adopting epistemic reductionism. I use Jonas Olson’s work as exemplary of moral error theory. I demonstrate that Olson’s argument that the rhetorical authority of moral claims is best explained by the error theorist’s conceptual claim applies equally in the epistemic case. Olson attempts to avoid this by claiming that epistemic claims are reducible to claims about whether our doxastic attitudes live up to their functions. There are two problems with Olson’s argument. Firstly, functional reasons are a species of a common genus – standards reasons – and since Olson’s authority argument against moral reductionism applies to standards reasons, it applies to functional reasons. Secondly, Olson’s claim that we cannot also cast moral reasons as functional is under-supported. I suggest that there is plausible evidence that we can and undermine his arguments against this claim. I do not argue that the epistemic companions in guilt strategy demonstrates the falsity of moral error theory. Rather, I argue that the Disparity Response to the epistemic companions in guilt strategy fails. (shrink)