Are moral standards simply social conventions?
The need to prove that another standard for our culture is better is your burden, not mine. The traditional morality of America, the one hated so badly by liberals, the historical default standard of America is the one I will stay with until someone can 'prove' they have a better one.
I will repeat what I said before.
Evidence that what a culture thinks about its foundational reality is very important and distinctive is seen in the freedom and prosperity of that culture.