That’s the basis for the case of free markets Hayek uses in The Fatal Conceit. He points out that morals developed in a similar way as behaviors in a free market—not from a rational, top-down design, but rather unconsiously evolving over great amounts of time to reflect actions that foster the survival and success of a group.

Laws tend to reflect morals. Morals of a given group tend to encourage behavior that has helped, and discourage behavior that threatened that group.

You asked for a convincing explanation of why sex is treated differently. I think an answer is that your construct is perhaps too limited. You should at least consider that since a sizeable portion of our society thinks prostitution is harmful, there may be some evolutionary accuracy to the idea.

However, I’m a free marketeer. So, I’d hasten to add that by knowing where morality comes from (essentially formed during our unregulated prehistory), it stands to reason that you should consider preserving, at least to some degree, a similar environment that grew the morals in the first place. An overly regulated society may ironically suppress its own ability to adapt a successful morality.

Really, you find that “coherent”? By what criterion is selling sex “self-harm”? He may be fully capable of determining for himself that selling sex would be harmful to HIM (provided that there would be anyone offering to buy sex from him), but by what standard does he define “self-harm” for anyone else who may be a prostitute?

That’s what I love about conservatives: The slippery utilitarianism. Just like their forebears, the early 20th century “Progressive” movement.