Disclaimer: I don't see prostitution as a men's right though I definitely think it would benefit society, I'm just curious about this topic.
In my country prostitution is legal on the prostitute side but not on the client side. On the left wing of the political spectrum, feminists are against a full regulation of "sex working" because they believe it's always exploitation of women. On the right side, christian conservatives are against it for the same reason plus for a matter of moral decency. But the majority of people (women included) in pretty much every survey I've seen are in favor of a full legalization. If we had to follow the will of the people, prostitution would be hastily legalized with no backward glance.
I suspect there's also a strong opposition from organized crime: they want to keep their profits out of taxation and they might as well actively finance a misleading propaganda. For example every once in a while you see books with titles like "Survey On The Johns" stuffed with phony "confessions" from Johns claiming that the real reason they go with hookers is because they get off oppressing and humiliating women by paying them for sexual services. Maybe I'm being too much of a conspirationist but I suspect those books are financed and promoted by criminal organizations for the reasons I listed above.
I understand that in the US prostitution is only legal in certain counties in Nevada. But my question is: who is lobbying against a nationwide legalization of the oldest profession in the world? and what are the real causes for their opposition?