This is not directed specifically at you, but people sound extremely ignorant when they make that claim. The founders certainly had that belief toward the federal govt but not towards the state and local govts. The founder belief in freedom was not a belief on individual freedoms that we profess today but the freedom of self governance. If you look at the way the 1st amendment was written it certainly is not a proclamation of the right to be free from religious based laws. Heck the right to freedom of religion didnt become a personal right until 1940. Thomas "wall of separation" Jefferson wrote a state law that castrated gays based solely on religious morality and he himself was probably an atheist. Just looking at the laws the founders created locally its plain as day they didnt intend our society to be secular but instead by be governed locally how the people saw fit whether that be secular or religious.
I do not mean to be rude but you do not have the best understanding of the topic.
1) it is not about "society" being secular. It is about the political institution of Gov't being secular. In essence these are one in the same but, you seem confused as to the meaning of "Secular".
Secular simply means - not a "Sharia/theocracy" That the laws of the land are not made on the basis of any particular religious belief and that religious leaders do not have political power/ power to make law based on religious belief.
Two of the main principles on which this nation was founded are
1) Individual rights and freedoms/Liberty are "Above" the legitimate authority of Gov't.
2) the authority of Gov't comes from "we the people" as opposed to "Divine Right"/God as was done in the past.
1) means that the Gov't is not supposed to have the power to make any laws outside its legitimate authority .... especially when it comes to individual liberty.
The power of the Gov't was to be LIMITED. Limited to what ? Protection from Harm ... direct harm one person against another (murder, rape, theft and so on).
I can delve more into this but to keep things short:
The legitimate powers of government extend to such acts only as are injurious to others. But it does me no injury for my neighbor to say there are twenty gods, or no god. It neither picks my pocket nor breaks my leg.
-- Thomas Jefferson, Notes on the State of Virginia, 1781-82
Under the "Social Contract" (Agreement by which we the people give Gov't authority the power to punish people) the powers of Gov't were to be very limited. If the Gov't wants to make a law messing with individual liberty it must appeal to we the people to change the social contract.
A change to this contract requires not 50+1. The bar is "overwhelming majority". This was to prevent what was termed "tyranny of the majority".
The reason slavery and anti-gay laws were allowed was because the overwhelming majority agreed. Thus these were legitimate.
2) I will let the founders speak on this one....
Millions of innocent men, women, and children, since the introduction of Christianity, have been burnt, tortured, fined, and imprisoned; yet we have not advanced one inch toward uniformity. What has been the effect of coercion? To make one-half the world fools and the other half hypocrites. To support roguery and error all over the earth.
-- Thomas Jefferson, Notes on the State of Virginia, 1781-82
Thirteen governments [of the original states] thus founded on the natural authority of the people alone, without a pretence of miracle or mystery, and which are destined to spread over the northern part of that whole quarter of the globe, are a great point gained in favor of the rights of mankind.
-- John Adams, "A Defence of the Constitutions of Government of the United States of America" (1787-88 )
As I understand the Christian religion, it was, and is, a revelation. But how has it happened that millions of fables, tales, legends, have been blended with both Jewish and Christian revelation that have made them the most bloody religion that ever existed?-- John Adams, letter to FA Van der Kamp, December 27, 1816
The idea that the founders wanted some kind of Christian version of sharia law/theocracy rather than secular Gov't is abject nonsense on so many levels it is not even funny.
Gov't is not suppose to make "ANY" law outside it's legitimate purview , never mind make laws willy nilly based on personal or religious belief.