Casual racism, when used appropriately, can be very funny and of course when creating the world of the 60's is entirely justified in the context of Mad Men. It is the evening Muhammed Ali/Sonny Liston 'phantom punch' fight, the guys of the office are psyched and in an offhand comment Don's elder secretary claims: "I don't see the point of it, if I wanted to see two negros fight I'd just throw a dollar bill out of my window."