It is the similar argument made for legalization of marijuana. What (besides the Christian viewpoint of selling your body) is really the issue with prostitution?
If it was legalized, it could be regulated with healthcare and all that other stuff that other countries do for their sex workers. It would eliminate or at least reduce the trafficking of humans, reduce crime, reduce the prison population, reduce illicit drug use (considering that those who are trafficked are heavy drug users in order to push away the pain of having to do such things under force).
Anywho...or he could have bot a sex robot