I ran across an interesting passage in Anson Rabinbach's In the Shadow of Catastrophe.
Since for postapocalyptic thinking "Auschwitz" now signifies the point at which the project of modernity reveals itself fated to culminate in barbarism, contemporary postmodernist thinkers unquestioningly regard it as legitimate to collapse the logic of modernity with the most extreme manifestation of politically organized terror. The event thus condemns not merely the bureaucratic and administrative procedures of the man-made apocalypse, but the ethical, technological, and political structures of the modern world. As Zugmunt Bauman has argued, "modernity" harbored two hopes: a single, anthropologically invariant self-identical subject capable of fulfillment and the utopian aim of transforming society in the image of perfection. When a uniform ideal of existence was imposed on any community, the willful surrender of traditional moral conscience was sanctioned. In this view, totalitarianism was made morally and politically feasible by the various "projects" of social homogeneity and social identity endemic to the Western ideal of rational society.
Rabinbach goes on to call these views into question--pointing to the role of historical trauma or the tragic consciousness in this cynical/tragic sort of formulation.
Certainly it is true that Auschwitz would have been impossible without Enlightenment Rationality and its more extreme modern relatives. However, the Nazis were hardly an extension of Enlightenment liberalism, but rather an intensely anti-rational reaction to it, aided by the proliferation of technology and bureaucracy. It seems to me that attacking Enlightenment liberalism on the basis of the terror of its achievements is to engage in a similar nihilism that has led to the Anti-Red, Anti-American, Anti-Civilization position of the fascists.
That said, the Holocaust is a real historical warning against technological hubris. Social "evolution" does not necessarily come along with advancements in the mode of production and technology--indeed they could lead to the opposite.