There is a very important distinction I think we need to make clear.
Government, as expressed in law, should have no moral system. Morals are not embodied in law. Ethics, are the province of laws.
The men who create laws, and who enforce them, need to be guided by morals in their conscience; and these morals should roughly accord with the laws they create and enforce, to the extent possible.
Further, these laws should roughly accord with the morals of those expected to live under them, to the extent possible.
NOT, to reflect in law all that which any may believe to be moral or immoral.
Our nation exists for the sole purpose of, and with the sole authority and validity of, preserving the fundamental rights of man against those who would abrogate them.
The day we forcibly encode a specific religious moral system into law, is the day we cease to have any validity as a nation.
We were created, chartered, and draw our authority to be a nation, and execute those powers delegated by our citizens; from a constitution which specifically prohibits us from doing so.
If you believe we already do, or seek to prove we have always done so, you are a fool at best, and a danger at worst.