The Man works alongside a labourer who comes from a... (thinking how to phrase it politely) ...uhm, troubled background. Most of his family you probably wouldn't ever meet in a library and everyone seems to both owe money to someone and also be owed money to.
But, anyway: whenever the labourer does something for The Man, The Man thanks him. It's what The Man does: even if what the labourer is doing is part of his job description, The Man still thanks him. It's, like, if someone's being nice to you, say "Thank you" to them. Easy.
But now imagine the situation below.
The labourer comes up to The Man one morning and asks that The Man stop thanking him. Apparently, the habit's catching: the labourer has started saying "Thank you" to his flatmates, too, and his flatmates - who are, by the sounds of it, from as troubled backgrounds as the labourer himself is - have promptly told him off for doing it. They've gone, mate, why the f*ck are you saying thank you? Stop the f*ck doing it!
The Man listened to the labourer's concerns, thought for a moment, and replied, "F*ck off."
To which the labourer replied, "Well that's better!"