In Psychotherapy, one of the key ideas is that of "splitting". The notion is that many people, perhaps most, divide the world into sharply opposing categories, corresponding to the "good breast" and the "bad breast", representing, apparently, some failure of integration in infancy. You can see this kind of thinking in fairy tales- the good witch and the bad witch. Splitting is the psycholgical basis of most popular films, and it also permeates the House of Commons...