Earlier quoted context omitted.
How... does that follow? To reduce slavery, legalize prostitution? There must be some steps in between I am missing.
Legal prostitutes can call the police for help from pimps or others trying to abuse or coerce them, without fear of arrest. Legal prostitutes are incentivized to work with the police to report others being coerced, it’s competition. Bringing things out into the open helps clean them up. Keeping them in the dark allows evil to multiply. The next time Prohibition helped the people it was trying to protect will also be…
Which is why the Prohibition thing rings false with me, especially the alcohol one. Alcohol was pretty much enjoyed by everyone to various degrees. Buying sexual services, while popular, not as much. So it's an analogy, but not the greatest. (Also ignoring that most sexual services are bought by men, while alcohol was/is used to a much larger degree by both sexes.)