Adrian, this post, I hope, will isolate the essential nature of our differences on this topic:
From Wikipedia: Moral rationalism, also called ethical rationalism, is a view in meta-ethics according to which moral principles are knowable a priori, by reason alone. Some prominent figures in the history of philosophy who have defended moral rationalism are Plato and Immanuel Kant. Perhaps the most prominent figure in the history of philosophy who has rejected moral rationalism is David Hume.
The opposing hypothesis offered by Hume has been lately labeled the "Intuitionist Model" I agree with Hume and recent science is headed toward support of his hypothesis.
If the rationalist model is correct, you're right and I'm wrong because the rationalist model asserts that moral principles can be taught and learned. Therefore, it's potentially possible for the moral guidance offered in scripture to be useful.
If the intuitionist model is correct, I'm right and you're wrong. If I'm right, all the moral guidance created by reason, whether it's in the form of criminal laws, philosophical ethics, or sacred scripture, is sometimes coincidentally right -- the way a stopped clock is right twice a day. It's right only when it agrees with our conscience. And, when those creations of reason are in conflict with conscience, they are potential biases.
The best example of the Christian Bible's moral guidance in conflict with conscience I can think of happened in 1866. This was almost two centuries after, in about 1700, the nations of the world had begun to abolish legal slavery. Pope Pius IX, leading his huge Catholic contingent of Christians, said he found nothing in divine law against the buying, selling or trading of slaves. The point I want to emphasize is that according to scripture, this pope was right but, morally, he was wrong because his judgment was biased. The men who wrote that scripture were from an earlier age and a morally immature society. Consequently, they condoned the practice of slavery.
So, how could those men from an earlier age, citizens of a morally immature society, offer moral advice that would motivate moral progress yet condone slavery and the treatment of women as property? You may consider the question rhetorical.