Another argument against the legalization of prostitution is the moral decay that normally follows such an action. While one can logically argue that America is not the moral bastion that it once set out to be, it still maintains many ties to Judeo-Christian morals. Do we really want to legalize a practice which promotes adultery, lasciviousness, and often the degradation of women? While many "legal" prostitutes say that they chose their trade, they also admit that it is not their first choice and hopefully will not be their last.
If you study history, you see that the moral bankruptcy of a civilization most often leads to its complete downfall (the Roman Empire, the Jewish Kingdoms--on several occasions, etc.) One would be hard pressed to prove that prostitution does not fall within the realm of immoral activity.