I’m just going to answer a few questions from a member of the studio audience.
Identifying a person who would torture a child as somebody that people generally have many and strong reasons to condemn is captured in the moral statement, "It is wrong to torture a child." From which it follows that I or you should not torture a child.
How does it follow? Remember, "[t]o say that S is prescribed for A, but A has no reason for action to bring about S, is incoherent". From the fact that "people generally" have good reasons to oppose child-torturing does not imply that you or I have reasons for action to stop child torturing.
Because moral claims are not prescriptions for the individual they are addressed to. They are prescriptions for people in general. A moral claim is a claim that people in general have reasons for action to bring the forces of praise and condemnation to bear on a particular desire.
They are also, at the same time, prescriptions against the agent insofar as it is the case that people generally have reason to deliver praise, condemnation, reward, and punishment to that person. However, moral claims remain true in virtue of the reasons that people have to deliver praise and condemnation.
The key point is not that people in general condemn something, but that normative people do, and we are that.
Actually, the point is that people in general have many and strong reasons to, whether they actually condemn it or not. I have already mentioned how false beliefs and bad desires (desires that people in general have reason to inhibit) sometimes cause people to do that which they do not, in fact, have sufficient reason to do.
To move from description of desires as "good" to prescription of actions that "morally good" implies, you need something more. You need to bridge the gap between practically-should and morally-should, or your theory is not prescriptive.
Practical-should claims are prescriptive. In fact, they represent the only type of prescriptivity that is real. Moral-should is a species of practical-should. It is concerned with the practical-should of bringing social forces such as praise and condemnation to bear to promote desires that tend to fulfill other desires, and inhibit desires that tend to thwart other desires.
There is no gap for me to cover. The gap that you write about is as fictitious as God and angels. The demand that a moral theory include an account of this gap is as misguided as the demand that evolution include an element of intelligent design.
[Desire Utilitarianism] logically ends at "Those reasons give them reason to bring the social tools of condemnation to bear against those whose desires are such that they would torture a child." It cannot bridge the gap and be descriptive without further assumptions. I agree that people would generally also have mistaken beliefs and so on, but even brushing all these problems away for now, DU only gets that far.
There is no place further to go. Desire Utilitarianism stops at the boundary between 'is' and 'is not' - the boundary between fact and fiction. That is as it should be.