I worked with a black teacher, quite the gentleman. He took Thai lessons in his free time, and when he realized what Thai people were saying about him, he confronted them in their own language. That didn't slow them down one bit, they just kept trash talking him.
As well, I know of a school director in charge of six large schools, and she has put the word out in no uncertain terms they are NOT to hire black teachers, regardless of how desperate they are for teachers or how qualified the teacher may be.