derivative of the Calvinist belief: either you’re elect or you’re irredeemably evil. there’s little point in moral instruction because you’re already either elect or not.
you simply lack the moral spine to do right, is the thought. you were always doomed to be lost.
in practice, the lefties are more diligent, more conscientious, have more self-control. they marry for longer and engage in less vice. the difference is that while the right honors self-improvement, the left actually secretly despises incompetence.