The Bible vs. the Heart
The other modern substitute for the Bible is the heart. We live in the Age of Feelings, and an entire generation of Americans has been raised to consult their heart to determine right and wrong.
I've heard too many people justify their positions based on their feelings, to the point that they refuse to even consider logic, reason or evidence. The irony is that these same people are frequently also atheists, who hold themselves to be morally and ethically superior to people of faith because they claim they are the ones who are rational, logical and reach conclusions based on evidence.