Why is Robin disgusted with David? What does this say about Scotsmen?

 Robin wished to see David because he had known a surgeon whose last name was Balfour. David was ashamed to admit that he knew nothing about his relatives so he could not tell Robin whether he was related to the surgeon. Robin looked disgusted and rose to leave without excuse, when Alan walked in. The two stood face to face, glaring at each other.  Apparently this is supposed to show Scotsmen as demanding and unfeeling.