A superb illustration of the theory of collective security–in which an attack on one is an attack on all. From an individual and group level, it helps to have a common objective, even an enemy. In this case, Jonathan Haidt calls them “asteroids”:
A basic principle of moral psychology is that “morality binds and blinds.” In many pre-agricultural societies, groups achieved trust and unity by circling around sacred objects. In modern societies, much larger groups bind themselves together by treating certain books, flags, leaders or ideals as sacred and by symbolically circling around them. But if your team circles too fast, you lose the ability to see clearly or think for yourself. You go blind to evidence that contradicts your group’s moral consensus, and you become enraged at teammates who suggest that the other side is not entirely bad (as New Jersey’s governor, Chris Christie, is now finding out).
Unlike a foreign attack, a problem that threatens only one side’s sacred values can therefore divide us, rather than unite us. It’s as though a giant asteroid is headed for the Earth. One side sees it coming and screams, but the louder it screams, the more stubbornly the other side covers its ears and averts its eyes.