Even if you are morally opposed to prostitution, is there really any benefit to authorities when you remove a centralized location and move it to the street or many different websites? If you really want to manage the prostitution "problem", having it all on a single website seems like a benefit for managing and researching the issue.
Most sex workers agree that their safety is improved dramatically by having the business side of it out in the open. And, there have been studies on sex worker safety that indicate strongly that legal prostitution is safer for everyone; it also reduces coercion when it is not underground (women don't need a pimp, if law enforcement is on their side). Since I started paying attention a few years ago, I've noticed that…
On one hand, there are those who believe that conducting these arrangements in the open is safer for all involved parties.
On the other hand, there are those who believe that sex work can never truly be consensual, because even if consent is given, a sex worker may have felt pressured to seek this life because all other choices available to them to make a living and attain food and shelter were sub-par or nonexistent. This argument supposes that given a different, idealized circumstances free of such pressures, few people would choose sex work.
I find this argument very similar to the idea of age of consent, in which society declares that people below a certain age are incapable of informed consent, and similarly, the widespread societal taboo against suicide, which implicitly suggests that no rational person free of undue pressures would consent to ending their own life, therefore anyone who commits suicide was pushed to do so by serious factors that impaired their ability to properly consent.
Finally, there are those who just want to be 'tough on crime', and actions like this fit the bill at first blush, while letting it operate would be construed by the same population as inaction.