I don't like it that Jhaniah says she won't see black guys, but I think it is fairly common for escorts to be more wary of new clients who are black. And even though I don't like it, and would prefer she try to figure out if the caller is a gentleman, I do think it's her right to set her limits and at least she is up-front about it.
Escorting is a business and -- usually -- nothing personal. Escorts want to maximize profits and minimize trouble. I really don't think it's racism to be more wary of a particular group since it's based on experience.
I know a little about this because the two TG escorts I know rather well for years have discussed it, and it's pretty much what Wendy and Vanessa said. And keep in mind, these (referring to the 2 girls I know) are both black TG escorts ! You wouldn't normally think a black person would be racist towards another black person.