My favourite Orwell quote, almost every day something brings it to mind.
“The point is that as soon as fear, hatred, jealousy and power worship are involved, the sense of reality becomes unhinged. And, as I have pointed out already, the sense of right and wrong becomes unhinged also. There is no crime, absolutely none, that cannot be condoned when "our" side commits it. Even if one does not deny that the crime has happened, even if one knows that it is exactly the same crime as one has condemned in some other case, even if one admits in an intellectual sense that it is unjustified -- still one cannot feel that it is wrong. Loyalty is involved, and so pity ceases to function.”