Only a couple of times have I ever had the opportunity to really ask a non-believing conservative what they based their moral universe on. One had no real answer and didn’t even try, the other said that his world view was based on right and wrong, not God.
When I tried to ask him who decides what was right or wrong, he answered that people know what is right or wrong naturally. He then started some drivel about evolutionary selection of altruism. But the conversation must have made an impression on him, just a few years later he called me and told me that he had become a Christian, and that he had looked me up because of the talks we had had.
Good for him.