>The notion that moral judgments are not just true or false claims about human conduct helps explain the failure of ethical theories as far back as Aristotle’s. These theories started out on the wrong foot, by treating morality and immorality as intrinsic to the actions themselves, instead of our responses to them.
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Factoring human emotions into moral judgment explains much about them. Why they are held so strongly, why different cultures that shape human emotional responses have such different moral norms, even why people treat abstract ethical disagreement by others as a moral flaw. And most of all, this meta-ethical theory helps us understand why such disputes are sometimes intractable.

Basically, this is emotivism-the idea that statements of moral value indicate nothing more than personal preference, and implore the listener to agree.

Rosenberg is known for being a brutal nihilist who completely rejects the idea that morality exists, and claims that the only thing that causes us to be "good" is a "core morality" we mostly happen to share intuitively. His book The Atheist's Guide to Reality is a good read, even though I agree with very little of it.

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>Still another way of attempting to justify moral judgments goes back to Aristotle: What is morally right is what virtuous people do. We can see what is morally right by observing how virtuous people behave. The very existence of honor killing reflects the problems this approach faces. The practices one culture identifies as vicious are virtues in other cultures. And there is no culture-free point from which to adjudicate such disagreements about what counts as a virtue.

This isn't entirely accurate-Aristotle doesn't claim that virtuous actions are "morally right"-he had no concept for morality divorced from reality the way we do. Virtuous actions are just that, virtuous. They lead to eudaimonia, the state of human flourishing in which a human is living in accord with their function to the greatest possible degree.

Aristotle recognizes the fact that different cultures have different ideas about what constitutes human flourishing, but he doesn't take this challenge seriously-they merely describe different forms of good citizenship in relation to a different polis, and (depending on the polis) good citizens are different from good men.

Aristotle is wrong about many things (slavery, women, physics), but he's not wrong about the idea that there are certain behaviors which lead to a more harmonious, happy, and effective human life, and the capacity to engage in those behaviors constitute virtues. He believes that if you're temperate, courageous, prudent, etc. you will have lived a better life than if you didn't have those virtues. You can say he's wrong about that, and there are certainly problems with his virtues, but it's hard to deny that it's better to be cowardly, bad at decision-making, prone to addiction, etc. If you want to argue that's true, I'd wonder in what sense you want to claim it's true, because it's not in any sense relevant to actual, day-to-day human life as far as I can tell. That's Rosenberg's problem, in my view-he's concerned with morality rather than virtue, and if you're concerned with a metaphysical morality while also having a materialist ontology, nihilism is your only real option.