Taking the racism thing as a discussion.
In general, as a service provider, where does a wg (any of them) separate the personal from business? Lets face it, despite what they say, its not a yearning for cock that has them working. Its a job, I'm sure few would date me for free, yet a few notes has them all at it.
I am not racist, some are, many are somewhere between. I can see how the girls who are very focused can completely separate the business side and provide for all shapes/sizes/types. The good ones do it without you knowing.
As a guess, the ones who state "due to bad experience" are looking for polite way of refraining as I bet a fair few white guys leave bad experiences.