Why is this constantly said about atheists and agnostics?

Much of what pes for Christian opinion is nothing but extreme narcissism. "I have all the answers (because the Bible told me so), but you're ignorant." I'm moral, but you aren't." "I'm on God's side, but you aren't." "In short, I'm better than you." This kind of narcissism often erupts as wars against the infidel, at which times individual narcissism becomes social pathology.