It is a fallacy to assume that, if a specious moral argument is advanced to justify some practice, then any other moral argument that would justify that same practice must also be specious. Consider, for example, the following argument: Social Darwinism has been used to justify war; Social Darwinism is specious, and thus so is its justification for war; therefore, war cannot be morally justified. The final statement betrays the fallacy, because the fact that war is not morally justified by Social Darwinism does not imply that it cannot be morally justified by some other argument. This fallacy can impede moral progress, because if we assume that a certain practice must be immoral because a specious moral argument was previously used to justify it, then we will automatically reject new arguments that seem to justify that same practice, without ever taking seriously the contents of those arguments. Yet it is only by taking seriously and critically assessing the contents of such arguments that can we rationally assess their validity, and recognize whether they pave the way toward moral progress.