What Madison wrote was that a “perfect separation” between Church and State was preferable, both being kept more pure the more they were kept apart as far as in determining actual governance rather than in informing a personal morality.
What made the USA different than any nation that came before was not adherence to a religious doctrine, not an insistence that the State enforce religious rather than civil morality; but that the citizen was sovereign over a government of limited and enumerated powers and that the natural rights of the citizen would be recognized, including the right to freedom of conscience.
Our Constitution was written for a religious and moral people. But it was not written so that Government could enforce either a religion or a religious morality.
Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience.
— C. S. Lewis
From Thomas Sowell’s favorite quote page.
Learn it. Live it. Love it.
You did, by default.
Without a commitment to the transcendent there IS no concept of "natural rights."
You quote Lewis to propose ANY morally based constraint is bad, when that is, like anything else touched by the libertine, a corruption of the intended good.
I already conceded a religious government without limits is like the Taliban. You keep fighting, because you correctly infer your position is inherently dissonant. You can not excise the moral without losing the sublime rights our form of government recognizes.