I don't consider it racist to choose who you will or will not sleep with. What about those that won't see under 40 or 30 year old? If a provider doesn't want to see white guys, I wouldn't call her racist, I would just look elsewhere. Every woman has a right to choose who they WON'T sleep with. I think it's a good thing that they state it in their ads. If prevents wasting time and possible later confusion.
By the way - I don't see very large (BBW) women. Isn't that discrimination also in your terms? People have preferences. I bet you have women you don't even consider to visit the in the hobby, isn't that a similar situation. Why can't providers state their preferences in their ads. To me your post is more about stirring contraversy.