My husband's former bulldog went to work with him every day. For a while, he worked with a man from Nigeria, who would tease the dog all the time. My husband swears that from then on, Roxy did not like black men.

I don't think you can really call it "racist" ... dogs just associate certain characteristics with people who look or sound similar. I had a lizard who hated people who were wearing hats. My dog Pepper LOVES older women, but HATES children. Lucky loves and wants to go with anyone in a truck. I happen to know she used to belong to an over-the-road truck driver and went with him on his routes. If I didn't know that, though, I might think she just especially loved men, or people wearing baseball caps, etc.