Did you know distributing information about birth control used to be a crime? So was divorce and interracial sex/marriage. All of these things were once illegal because they were deemed a threat to society. Then we came to understand that they're morally neutral personal choices, and laws about them changed. I believe prostitution should join that list of decriminalized behaviors.
Society has a duty to protect the unwilling and the underage from sexual exploitation. But we have other laws for that. I'm a fully cognizant adult, and I own my body. If I choose to consent to sex with another adult for any reason, then absent any force or coercion, the government should have no right to say my reason for consenting is unlawful. If it's not illegal for me to have sex with someone because he bought me an expensive dinner, it shouldn't be illegal for him to just give me the money.
You may think being (or being with) a prostitute is an example of self-destructive behavior. I disagree, but even if you were correct, people have a legal right to engage in other potentially self-destructive activities. I can gamble away my paycheck on state-sponsored Lotto tickets and live on nothing but cigarettes, Twinkies, and Jack Daniel's. Should I be arrested for doing those things? Do you think that would help me?
I use the comparison to tobacco and alcohol advisedly. Like other adult behaviors, there should be rules about prostitution. I'd frame it like this: If a sexual act would not be illegal if no money were exchanged, then the exchange of money shouldn't make it criminal. Thus, laws protecting the unwilling and the underage stay in place, and laws about public sex/nudity, trespassing, and general nuisances would address concerns about street solicitation. Prostitutes would get business licenses and pay taxes. Their licensure wouldn't be punitively difficult or designed to stigmatize them. Their tax revenue, together with money currently spent investigating and arresting consenting adults, would be directed toward helping the truly victimized.
If you find prostitution distasteful, then you shouldn't engage in it. But most people have to work at something to earn a living. In my experience, having sex for money was infinitely preferable to waiting tables or being a cashier. Any human interaction can be positive or negative, depending on the people involved. Take marriage: There's nothing bad you can say about prostitution that can't also be said of the institution of marriage. Was it historically a system of ownership of women? Yes. Are some wives abused by husbands? Yes. Are young girls forced into it for financial reasons? Yes. Those things happen. Nevertheless, we don't outlaw marriage, because for some people, it's a positive choice. There are always ethical subtleties when it comes to sex. But the government shouldn't have control of what I do with my body. And it certainly shouldn't be in charge of sexual morality, as it is spectacularly ill-equipped for that task.