The man in overalls would probably has said the same thing if the waiter was white. I am from the south and often was referred to as boy. Get a life.
This is true. Nothing is thought of it when grown men (white, black, whatever) are called “son” or “boy”, but mostly by people who know them, like a man tells a tall tale, and the man listening says, “Aww com’on son, you know that ain’t nothing but a tale”.