>> Sex is one of the last places where women have more power than men.

It's interesting that you point that out. Some claim that plenty of women use their sexuality to manipulate men, to trade sex for resources (marriage), and other such things. By legalizing prostitution you deprive the rest of the women from being able to do this - guys don't have to buy the cow when they can get the milk on an as-needed basis for a negotiated price and no strings attached.