That doesn't help too much with classifying things into categories of "right" and "wrong". Either one defines these terms as relative to some unspecified agent's preferences, or one gives them a naturalistic definition - e.g. as the preferences associated with universal instrumental values. Then there's the issue of which type of definition is more practical or useful.
My point a few comments ago was that moral realism is the theory that moral statements are real, not that statements about morality are real. Statements about unicorns are real: "unicorns are cute white horses with pointy horns that can only be seen by virgins" is a real statement about unicorns. Unicorns are NOT real.
Any argument or disagreement in this chain arises from what is purely some sort of disagreement about how to use some terms. I don't mean to suggest that the content of moral realism or normative vs descriptive is right or true o...
Do you believe in an objective morality capable of being scientifically investigated (a la Sam Harris *or others*), or are you a moral nihilist/relativist? There seems to be some division on this point. I would have thought Less Wrong to be well in the former camp.
Edit: There seems to be some confusion - when I say "an objective morality capable of being scientifically investigated (a la Sam Harris *or others*)" - I do NOT mean something like a "one true, universal, metaphysical morality for all mind-designs" like the Socratic/Platonic Form of Good or any such nonsense. I just mean something in reality that's mind-independent - in the sense that it is hard-wired, e.g. by evolution, and thus independent/prior to any later knowledge or cognitive content - and thus can be investigated scientifically. It is a definite "is" from which we can make true "ought" statements relative to that "is". See drethelin's comment and my analysis of Clippy.