Couple of things:
1. Who a woman (or man) chooses to see is absolutely no one else's business. Publicly or privately. Whether it is something that she keeps to herself or publicly shares, still no one else's business.
2. Unless you've been a woman in this world, let alone a sex worker, do you really have any idea or experience the shit woman go through? Men at best are obtuse in this manner and cannot relate even with the best of intentions, regardless of age.
3. One bad/unsafe/aggressive/rude or disrespectful experience can traumatize a person for life.
4. This whole debate is not about discrimination or specifically racism. It is about respecting a persons' choice and boundaries (even if you can't relate or understand). Simply Show some respect and move on... You are not applying for a job, you are asking another human being to share time, intimacy and sex with you... Kinda not the same.
5. Do you really think that an agency would publish this information if it wasn't for the comfort and peace of mind of their ladies? They are willing to filter in the interest of safety and comfort levels (and yes I personally have known some sex workers over the years that were robbed at gunpoint/knife and aggressively touched or "manhandled").
Scarred for life.
6. There is definitely a statistical correlation between certain cultural groups (not just skin colour) and general behaviour/approach to women. Sorry, but true. I also know women who won't see Greek or Italian men (and they are white btw).
7. Don't we/you have more important things to do?
8. Finally, a harsh truth, just because you have an opinion, doesn't mean its valid or true. Too many people in general talking yet no one actually saying anything meaningful.