[helloworld11]

I'd argue that the answer to this fundamental question is fairly simple: Does your specific instance of a certain activity have an extremely high likelihood of causing immediate or rapid and obvious, direct and quantifiable harm to others? If not, then prohibition should be tabled away. I'd also personally argue moral constraints on prohibitions under the rubric of basic individual rights to do things that don't verifiably and materially or physically harm others but in purely utilitarian terms, my first point is a good metric in my view.

There of course also activities that individually cause little to no harm but which in the agregate are dangerous for society as a whole. In these cases. I'd argue that long-term total effects and difficulty of enforcement should be balanced against a likelihood of mitigation strategies being effective without resorting to outright individual prohibition, but that's a complex question in general. In any case, for sex work, it doesn't even enter the picture, except for on the question of enforcement of prohibition (which has never worked for prostitution and shouldn't be applied anyhow).