Another comment from the studio audience.
How is this not simply a metaethical error theory (there are no moral facts, strongly construed), combined with an attempt to reconstruct something "almost as good" as morality? . . . For example, someone who held this position might say that there are no moral facts as people generally construe them, since there are no categorical prescriptions, and that is an ineliminable part of standard moral discourse. However, insofar as we form a community of people who care about other people's welfare, there are certain "moral-like" imperatives that apply to us because of that fact.
Well, I would accept that if it were the case that categorical prescriptions were an ineliminable part of standard moral discourse, then it would follow that desirism is an error theory combined with a proposal for something "almost as good" (though I would argue that it is, in fact, significantly better than the fiction and myth of categorical prescriptions).
As it turns out, I reject the antecedent. I hold that people invented and embraced morality because they saw in it a significant potential for realizing those states of affairs in which the propositions that are the objects of their desire-states are true.
They did not fully grasp what it is exactly that had this great potential. Some suggested that they must be categorical imperatives. However, we have to reject this option because categorical imperatives, in virtue of the fact that they do not exist, do not have any potential to help people in realizing their desires.
So, categorical prescriptions - far from being an ineliminable part of moral discourse - is a theory about the nature of what has this great potential that can easily be eliminated in virtue of the fact that categorical prescriptions do not exist.
Furthermore, I don't think that there is any such thing as an ineliminable part of discourse. Language is an invention, and we can do with it what we choose. If chemists can elminate "having no parts" from the definition of an atom, and biologists can eliminate "bad air" from the definition of "malaria", then ethicists can eliminate "categorical prescriptivity" from moral terms.
Still, as I final point, I do not think that this question is worth a great amount of debate. If somebody wants to insist that moral terms, to them, refer to categorical prescriptivity, I do not need to argue that this fails to correspond to the public use of the term. It is enough to argue that 'morality' understood this way does not exist and, as such, it has no relevance in real-world decision making and is not worth bringing up as if it is relevant to any choice being made.
Whereas desires that people generally have many and strong reason to promote using rewards such as praise and punishments such as condemnation are very real and are very much worth bringing up when discussing real decisions that are to be made in the real world. The fact of these desires are particularly relevant to decisions governing the use of rewards such as praise and punishments such as condemnation.
I have "real" and "of great importance in real-world decision making" on my side. You can keep "categorical prescriptivity" and, in keeping it, render all of your moral claims false and irrelevant in the real world.