We believe that it is necessary to know as much as possible about the behavior of the individual and about the simplest forms of exchange….Economists frequently point to much larger, more “burning” questions, and brush everything aside which prevents them from making statements about these. The experience of more advanced sciences, for example physics, indicates that this impatience merely delays progress, including that of the treatment of the “burning” questions. There is no reason to assume the existence of shortcuts. [My emphasis.] [John von Neumann and Oskar Morgenstern, The Theory of Economic Games and Behavior, as quoted from The Internet Archive.]
So we promptly assert the existence of a shortcut anyway, assume, for example, that nations are billiard balls, and say things like “Iranians only understand the language of force,” the type of argument that is wrong because it ignores individual variation, is wrong because it ignores adaptation, is wrong because it implies without evidence that the assertion would if true somehow distinguish Iranians from everyone else, and is wrong because alternatives have been discounted without being tested.