A black man starts work on a construction site. The other workers nickname him "Wog".
Feeling upset by this, the black man goes to speak with the foreman. The foreman laughs and tells him, "But we all have nicknames. We've got Mick and Paddy, they're Irish. Wac from Liverpool. And Mack from Scotland".
The black man was still not happy, so the foreman shouted at his men, "Mick, Mack, Paddy, Wac leave the Wog alone!"