"If I had to choose between betraying my country and betraying my friend, I hope I should have the guts to betray my country."
This is a famous quote by W.H. Auden, though the context you provided (about finding a common denominator among admired people and laughter) is not associated with this particular quote.
It's possible you are misremembering the quote or its context. Do you remember anything else about the book or its author?