Don’t let him pull you in – but – if the son-of-a-bitch socks you – let ‘im have it.

– John Steinbeck

Of Mice and Men, Chapter 2, George to Lennie about Curley. George is afraid Curley will hurt his friend and advises him to keep his mouth shut and go to the other side of the room whenever Curley is around. But if Curley punches him, he is to let him have it.