I don't really understand what the hang up is about prostitution. A lot of this seems to come from the idea that 'good women' don't have sex. I agree that nobody should be forced into prostitution, but in terms of physical labor, I don't think sex is all that much different than hard physical labor, and I don't see anybody pushing for banning digging ditches.
What? Digging ditches wouldn't directly enable an underground human trafficking world; I do not see how those are remotely the same. To act like opposition to the legalization of prostitution must hinge on some type of paternal sexism seems quite far-fetched.