Morality - Why bother?
Unless we assume that there is a God that either punishes or rewards us for our cruelty/good behavior, why should we act in any "moral" way at all?
A common reply will be "what if everyone acted that way? Then it would be worse for everyone!", but while this may be true, it doesn't prevent ME from being an total asshat, simply because me acting in one way doesn't automatically turn everyone else into asshats (it may encourage it, but why do I care?).