This is a question that walks the fine line between pragmatism and philosophy.
Ideologically, the only imperative to outlaw prostitution is the moral one. There is nothing inherently socially destructive to exchanging money for sex, or vice versa. It is documented in the animal kingdom, and operated on a sacred level in ancient human cultures. It is defined as evil and sin on the basis of religion and extremism for the most part. Since the moral views of any given group of people are not normative to all of humanity; and since moral beliefs contained within a single society can themselves be immensely varied, it is an act of inequality to legislate solely to pander to these specific groups. Surely, there are women in the world who actively and joyfully choose to sell their bodies- many have testified to this in the public eye. It is not our place to shame or condemn them; it our place to enable them to live their lives safely, while simultaneously protecting the public health. Further, from more logic-driven standpoints, the argument is actually very strong FOR prostitution. If you believe in self-determination, it should be a right. If you are a feminist who believes that women can choose to do whatever they wish with their bodies, this decision must be respected as well. If you’re a genuine free market capitalist, it probably seriously annoys you that it isn’t legal already- we know what the markets want! For Pete’s sake, look at the sale of porn and that’s only RECORDED sex. Honestly, consensual crimes create direct conflict between fiscal conservatism and social conservatism. (Maybe that’s why so many of them are grumpy all the time.)
Unfortunately, that’s just the theoretical side of prostitution. When you add in the real world, things get a little trickier. We do not live in a world where things are truly equal among race, class, and gender. Levels of inequality and sexism vary from culture to culture. However, there’s still an overall high dose of discrimination toward women in most countries, including the developed, Western ones. This includes both the hostile and benevolent varieties of sexism. Human trafficking is a very real phenomena that affects, by UN estimates, around a million people, primarily women and children, each year. Considering that the there are some organizations which help a certain percentage of people to exit each year, and that the life span of those people unable to leave isn’t estimated to be very long, you can see that there is a rather steady flow of human life into the business- and this statistic covers only physical trading of human beings. It doesn’t even touch on the more domestically relevant but virtual exploitation of children and women in pornography and on the internet. Even within legal prostitution settings, such as the brothels of Nevada or Vancouver, we know that many women in prostitution are still ruled by the orders of pimps, of all varieties- boyfriends, husbands, brothers, sisters, mothers, fathers, in-laws… On the street level (think: “street walkers” and internet escorts), the number of women working willingly and in conditions of just and safe employment are even more dismal. Within class issues, race issues also come into play. Women forced into prostitution are likely to be low-income, and minorities make up a disproportionate number of those entering forced prostitution, yet they tend to make less money and experience more violence. Pretty white women can easily fetch a rate of two to three hundred dollars (or more) for an hour, working for herself: while women of color may see as little as seventy an hour (split in half with a pimp… not exactly a fair pay scale, considering the division of labor involved.) The simple fact is that the culture surrounding sex itself doesn’t currently support the validity of prostitution, and until we make some major overhauls, it isn’t likely to do so.
The first step should be decriminalization, which is the next legal step, anyhow. Currently, prostitutes in most areas face strict punishments if they are caught, and considering how many people are there unwillingly, that seems like an unproductive way to stop the problem. We must focus on the prosecution of pimps and johns (especially those who trade in minors or women of “exotic” races). Concurrently, we must focus on equalizing resources for women (by giving them reasonable access to school, career training, and other exit resources.) I personally believe, very strongly, that the pool of women working in the sex industry will decrease substantially if global resources are made available. However, in the long run, professionalizing the institution of prostitution is probably in our best interests: though libertarians will cry about government over-reach, the fact of the matter is that the status of our prostitutes directly reflects our status of public health. Requiring them to have a working knowledge of how to put on a condom, and having the ability to negotiate safe and nonviolent sex, will cost society less in the long run.
Lastly, we shouldn’t encourage the glamorization of the industry. Even real women who choose to work in the industry can attest to its soul-wrenching nature; to present it in pop culture as though it’s “fun” or “progressive” would be misleading. When a woman is lucky enough to enter the business with the easy capacity to leave, she is truly privileged. Yet for so many women, it leaves a scar and basic distrust surrounding their souls. For this reason, we shouldn’t just encourage young girls to enter the lifestyle when we know it is toxic for so many. Another aspect we must acknowledge is that prostitution, at its base and current form, encourages dishonesty and pain. Unless we also accept the fact that not all human beings are meant to be monogamous creatures, we will only encourage cheating and faults of integrity. An entire campaign on the spectrum of healthy sexuality is needed to encourage ethical sexual behavior. Without coordinated effort and education on both sides- the so-called “pro” and “anti” sex movements- we will not move forward. Those who identify themselves as pro-prostitute should be organizing themselves, even forming unions, among sex workers, to demand fair and safe laws. And those who identify otherwise should be focusing on outs and advocating politically for better social resources lining up housing, education, and childcare choices for the women who wish to leave the industry.
In short… should prostitution be legalized? Yes, by all rational measures, it should. Are we anywhere close to doing that as a society? Not at all.