from Stephen Mulhall's review of Axel Honneth's "Reification: A new look at an old idea--The Berkeley Tanner Lectures":
It is not difficult to share Honneth's sense that the monstrousness of genocide is not adequately acknowledged by condemning it as immoral--a mere violation of ethical principle, as it were. But what the work of his critics should have helped him to see is that his own strategy also risks failing to acknowledge that monstrousness. For what makes genocide abhorrent is precisely that its practitioners did not mistake the ontological status of their victims. To be sure, they described those victims as racially inferior, as subhuman; but just as only human beings can be enslaved, so only human beings can be treated as subhuman. Indeed, recognizing that in this sense the Nazis knew exactly what they were doing is essential to grasping the distinctive evil of their inhumanity.
from Tamler Sommers' review of Jesse J. Prinz's "The Emotional Construction of Morals":
[Prinz's new book] argues for two related theses. The first is that our moral judgements are constituted by dispositions to experience emotions towards certain actions. To judge that cannibalism is wrong, for example, is to be disposed to feel a negative emotion--disgust, disapproval--towards the act of eating people. Prinz dubs his theory "constructive sentimentalism" because on his account, once we have constructed moral properties via our emotional dispositions, they become real, and we can perceive them. This allows Prinz first to resist moral nihilism . . . and second, to explain why morality seems like something that is "out there" in the world and not merely a projection of our feelings.*Prinz's second thesis is that we should embrace moral relativism, which he regards as a consequence of his constructive sentimentalism. Since moral judgements reflect emotional dispositions on the part of different people who have them, the same judgement may be true for one person and false for another. . . . Prinz correctly notes that being a relativist need not undermine moral motivation. Our values may not be objectively correct, but they are still our values--and the sentiments that constitute them provide us with plenty of motivation to act accordingly. Furthemore, while moral relativism does not entail a universal value of tolerance (if it did, it would be internally consistent), Prinz argues that it "make[s] intolerance difficult to maintain psychologically". The idea is that once you shed the notion that, say, "homosexuality is wrong" is a universal truth, you'll have a harder time wanting to stop same-sex couples from having equal rights. On the other hand, Prinz notes that our values may still motivate us to intervene in cases where one party is harming another against their will.
I have always thought of the Jewish holocaust as one of the strongest arguments for an "objective" theory of morality, i.e. there must be some universally valid standards of right and wrong, so that genocide is rightly and fully condemned for what it is. Reading Sommers' review of Prinz makes me think there is a plausible alternative to "objective" morals.
The evil of the genocide does lie, as Stephen Mulhall points out, in the fact the Nazis recognized the Jews as human and then went on to treat them as subhuman. The problem, I think, is not one of ontology but one of sentiment. Nurtured by centuries of anti-semitism and inflamed by Nazi propaganda, the emotional disposition to feel that Jews were subhuman were projected into "objective" values that validated genocidal actions. A people trained to view morals as relative--because everyone has a different emotional disposition and feels things different--might have inoculated themselves better than absolutist moralists against genocide.
Again and again, homophobia insists, "Homosexuality is just not natural," and no amount of rational argument can persuade it otherwise. Perhaps we should help homophobia see that it is a valid feeling (not an objective value), and other people, gay and straight, have equally valid, though opposite, feelings about homosexuality too. That may be a starting point for tolerance.