Sweden’s legal framework recognizes [the non-consensual nature of prostitution] by criminalizing the buyers and offering the prostituted a social-services exit strategy. This approach is premised on a human rights understanding that women and girls have a right not to be prostituted.Sweden imposes no criminal or civil penalties on prostitutes, reserving punishments instead for clients. The appeal of this approach is that sex workers sell their services because they're either coerced by ruthless organized criminals or because they lack decent alternatives in the more socially acceptable labor markets (I gather from the tone of the op-ed that Ramos would reject the possibility that many sex workers freely choose such work of their own volition). In other words, prostitution is not euvoluntary.
Let's accept that proposition. Prostitutes, for the sake of argument, are already on the fringes of desperation and they have little to fall back on. Clients, contrarily, are more or less randomly selected from all walks of life, including men who have a great deal to lose from a criminal conviction. One way for clients to respond to a threat of criminal punishment is to abstain. After all, low-cost pornography is ubiquitous, even in Nordic country. Another way for clients to respond is to insist on greater secrecy, more remote locations, &c. Part of the negotiations that result in a successful transaction will include security.
Greater security for clients implies less security for workers. A New Zealand brothel can hire bouncers to haul off violent riff-raff. A "legal" Swedish sex worker attempting the same will find herself with no clients whatsoever. Only the extremely stupid or the extremely well-connected would attempt to solicit such services. Swedish sex workers will either cater to those clients not already scared off by the threat of criminal sanction or they will be obliged to accept their by-definition worse BATNA. If we accept the premises of the op-ed's argument, the logical conclusion of criminalizing clients is doubly deleterious to the safety and health of sex workers: kindly, thoughtful clients will be driven out of the market, and the rowdy reprobates that remain will insist on more secretive locations for encounters, making assault, murder, and rape (yes, it is possible to rape a prostitute, check the language of your local statutes) more likely.
Ending prohibition seems counter-intuitive. But if there is a social interest in providing better opportunities for young women and men who seek jobs in the sex industry, allowing prostitutes to organize for their own safety and protection is necessarily an important element. Swedish statutes prevent the very thing they seek to accomplish. If the goal is to put already-troubled youth at greater risk, you could hardly design a more effective approach than to make patronizing prostitutes illegal.