Personally, I don't believe in the "racist" thing.
I do believe the dogs I've had were/are very attuned to the appearance of any person, until they become accustomed to said person.
When one lives in an all white household, in a predominantly white neighborhood, what does one expect of their dog upon meeting a person who looks entirely different?
Our dogs now, have no problem with our black neighbor, they like him when he comes over, as he did for Thanksgiving dinner. Then again, he's a nice negro, right?
I've had more than one dog, as I'm sure others on here have, that did not like folks in uniform. Coppers, Postal workers (reason to be afraid there?
), UPS, FedEx, Meter readers, etc.
Over the years our dogs have warned us of folks acting "weird", as in behavior that didn't seem what normal folks should be doing.
Had one great dog, never could understand why he did not like folks wearing hats. Given that I wear hats all the time, even indoors (I've got a ball cap on as I type this). Was he trying to tell me something? I was awfully tough on that dog for a few years.
But "racist"? Not mine at least.