Imagine if doctors, nurses, physical therapists, dentists... were free to reject patients because they didn't like them physically (color of teeth, too tall/too short...). Or if doctors ONLY took easy medical cases. Obviously society won't allow that. But many people who advocate for legalized prostitution want people (both genders) to be free to reject others for any reason. I don't understand that at all. If you're a professional, you ought to accept business from anyone who's respectful, has the money for what you're selling, and isn't breaking any laws. Why would discrimination in this industry be acceptable? The people being discriminated against are the people who most need the services they're willing to pay for.
Humans.