Erik makes a good point about common sense. Unless it's instinctive you can't know whether someone has been taught the same things as you or if they've been taught to perceive the same thing in a different way. In treating something as common sense, even allowing it to be called societal common sense, you assume that you share the same view. This indeed is exemplified in the movie; the man who says "Everyone knows that the people who live in those slums are no good" assumes that everyone shares his learned perception of urban poor. I would now append my earlier statement by qualifying instinctive common sense as common and societal common sense as based on assumptions rather than fact.