It is human nature to be moral because man is made in God's image, but since humans -unlike animals- are free moral agents, they are free to fo whatever they like, even to deviate from what comes naturally, but not without consequences.
Moral like when god ordered babies cut out of women's stomachs (God, the First Abortionist!) or when he said it was OK to beat slaves to death as long as it took a day or two to die or when he said take the virgin girls and forcibly make them your wives, meaning rape them.
Which of those is the morality to which you refer?