You know how when we meet a stranger and find out that person shares our background and our face lights up in joy. This person is one of us, he must be awesome. If we meet a stranger who is from a neutral background, we are cordial but not friendly. But if we meet a stranger and find out he is one of the others/enemy, we are suddenly on alert. We have to be wary of those people because those people always do this and that. The awesome person who shares our background might become Hitler or Stalin. The enemy or the infidel might become Gandhi or Mandela. But our face glows in a smile or turns into a frown based on their background, without finding out what kind of human beings those strangers are.