Scripture gets it's validity from itself, and understood through the Spirit when someone repents and believes in Christ.
We have choice, to choose good as opposed to choosing what is evil. Sin is an archery term, meaning, to miss the mark, the mark being God's standard, where it doesn't really matter if you miss by a millimeter or turn around and shoot in the opposite direction, it's still sin. We're all sinful, where no one does good, according to scripture. It's our will that is at odd's with God, and our choice to be so.
Explain how God allowing his creation the option to live in a righteous covenant relationship with Himself and telling us not to choose an unrighteous relationship, is God's fault? Given the presupposition that God created us, we can't say that's unjust, but, seems extremely just. Like, "If you stay with me, you'll live, if you choose pride and sin, you'll die." is not God making the choice, it's man, and if we didn't have choice to freely choose the highest good, he wouldn't have created us, because that is intricately interconnected to who God is and who we are.
Utilitarian morality is an oxymoron, that is, Utilitarian good and evil, because it's relative to either the herd or individual, which will always be immoral to the other herd or other individual. If you can find "Sum Happiness" it'll be in a reasonable ultimate ground, that is, God, as you can not derive an "ought to" statement from an "is". Whatever works, is not morality, as can clearly be seen, at least to me, by those who've practiced Eugenics and thought it was right, and those who've administered mass genocides and thought it was right. Utilitarian as that is for the herd, it's clearly evil.