"words should be used in such a way to maximize their usefulness in carving reality"
That does not mean that we should not use general words, but that we should have both general words and specific words. That is why it is right to speak of morality in general, and human morality in particular.
As I stated in other replies, it is not true that this disagreement is only about words. In general, when people disagree about how words should be used, that is because they disagree about what should be done. Because when you use words differently, you are likely to end up doing different things. And I gave concrete places where I disagree with Eliezer about what should be done, ways that correspond to how I disagree with him about morality.
In general I would describe the disagreement in the following way, although I agree that he would not accept this characterization: Eliezer believes that human values are intrinsically arbitrary. We just happen to value a certain set of things, and we might have happened to value some other random set. In whatever situation we found ourselves, we would have called those things "right," and that would have been a name for the concrete values we had.
In contrast, I think that we value the things that are good for us. What is "good for us" is not arbitrary, but an objective fact about relationships between human nature and the world. Now there might well be other rational creatures and they might value other things. That will be because other things are good for them.
But not everything people value is actually good for them. You are retaining the problem of equating morality with values.