But let's say we could get pasted the ethical boundary of controlling peoples rights over their own body. Making prostitution illegal does nothing to protect the legitimate women (and men) in the industry. By making it illegal you force people who want to work in the industry to have little to no legal rights: - If a client rapes or performs unagreed/unconsenting actions, there is no legal place to go for help - If a consenting prostitute discovers trafficking they are unlikely to report it because they have a distrust of the police - Legitimate people who would want/enjoy being in this industry stay out, making unground businesses resort to trafficking and abductions.
We already have a legal system capable of protecting and punishing those who kidnap, rape, abuse, molest and hurt other people. All criminalisation of any industry does is prevent participants from receiving government protection.