Many philosophers think that moral objectivism is supported by stable features of moral discourse and thinking. When engaged in moral reasoning and discourse, people behave ‘as if’ objectivism were correct, and the seemingly most straightforward way of making sense of this is to assume that objectivism is correct; this is how we think that such behavior is explained in paradigmatically objectivist domains. By comparison, relativist, error-theoretic or non-cognitivist accounts of this behavior seem contrived and ad hoc. After explaining why this argument should be taken seriously, I argue that it is nevertheless undermined by considerations of moral disagreement. Even if the metaphysical, epistemic and semantic commitments of objectivism provide little or no evidence against it, and even if the alternative explanations of ‘objectivist’ traits of moral discourse and thinking are speculative or contrived, objectivism is itself incapable of making straightforward sense of these traits. Deep and widespread moral disagreement or, rather, the mere appearance of such disagreement, strongly suggests that the explanations operative in paradigmatically objective discourse fail to carry over to the moral case. Since objectivism, no less than relativism, non-cognitivism and error-theories, needs non-trivial explanations of why we behave ‘as if’ objectivism were correct, such behavior does not presently provide reason to accept objectivism.