A young black boy is helping his Mother to bake bread in the kitchen when he gets flour all over his face. He spreads the flour around a bit and turns to his Mother and says, "Look Momma, I'm a white boy!"
His mother slaps him hard across the face and says, "Go and tell your daddy what you just did!"
The boy goes through to the lounge and says, "Look dad I'm a white boy!"
The father grabs the boy throws him over his knee and slaps his arse really hard and says, "Go tell your Granddaddy what you said!"
The boy trots off and finds his grandfather and rather sheepishly says, "Look mum I'm a white boy!" The grandfather grabs the boy, drags him to the bathroom, puts a block of soap in his mouth and begins to scrub his tongue with it before sending him to his room with no dinner.
Later that evening his mother calls him down to the lounge where his family are all seated and says, "Well have you learned anything?"
To which the boy replies, "Yeah I was only white for 5 minutes and I already hate you black bastards."