Hans Kelsen claimed that moral relativism provides the best foundation for democracy and that moral absolutism can only lead to authoritarianism. Other relativist theorists, like Schumpeter, Dahl and Ferrajoli, have defended a more moderate claim: that even if there is no conceptual or normative implication between relativism and the justification of democracy, both positions are at least compatible. This paper argues against both the stronger Kelsenian thesis and the moderate compatibility thesis. It holds, first, that if we understand what Kelsen calls philosophical absolutism or anti-relativism as a position that in meta-ethics involves some kind of moral objectivity, there is no conceptual connection between subscribing to this theoretical position and endorsing some kind of political authoritarianism or anti-democratic position. It also argues that in order to subscribe to the ideal of democracy as the most legitimate form of government, and given our social practice regarding the ideas of democracy and legitimacy, some kind of moral objectivity is required. The basic argument is that our practice presupposes the possibility of collective normative error concerning political legitimacy, that is, when we say that democracy is the only legitimate form of government we mean that this is the case in every country and in every historical era, no matter how the particular people in each case perceive their actual government. In particular, that would be the case even if a majority of the people in a particular country believed otherwise. This people would be in a situation of collective normative error, but this is something that meta-ethical subjectivism, and specifically relativism, cannot account for. Moral subjectivism can only understand political legitimacy in terms of subjective legitimation, which misses a central part of our current practice of the idea of political legitimacy, as well as an essential element of our normative ideal of democracy.