You’re starting with a libertarian premise most people don’t accept. The vast majority of the world accepts that it’s proper to restrict individual freedom even to protect people from themselves. Society has a role to play to help people make good choices and to make it hard for them to make bad or dangerous choices.
Also, you’re incorrect about the prevalent morals. Even in the US, women—who bear the lion’s share of the cost of prostitution—oppose legalizing by a large margin (50% to 30%): https://www.vox.com/2016/3/11/11203740/prostitution-legal-me.... And of course the overwhelming majority would still say it’s a bad or immoral choice, even if they agree someone should be allowed to make that choice.