Madison’s intent (or Jefferson’s or any one individual) alone isn’t relevant to legitimate legal interpretation. Originalism doesn’t rest on that (I think that’s what you’re driving at but could be wrong).
Here is the third amendment, "No Soldier shall, in time of peace be quartered in any house, without the consent of the Owner, nor in time of war, but in a manner to be prescribed by law". Does that mean the military can require an apartment or condo owner to quarter troops? How about businesses? It clearly says house. Do we agree originalism has issues without any context whatsoever?
Here is the sixth amendment:
In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the state and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the assistance of counsel for his defense.
It wasn't until 1963 that the Court noticed that last part, "and to have the assistance of counsel for his defense". I throw that in since he assumes the early courts read the document clearly and it was muddled later. That isn't so, it quite clearly specifies that a defendant is to have, "the assistance of counsel for his defense". There are zero ifs, ands, or buts. So early courts could make mistakes.
But to use his argument, nothing in the document gives the power for the government to create or enforce a religion. of any kind. In addition, article 6 clearly says there can be no religious test for any oath of office.
The Articles of Confederation specifically referenced God several times and the Declaration referenced God. Isn't that a sign of religious neutrality creeping into the founders? The document does not mention God one time.
And we did sign a treaty on this. The Treaty of Tripoli was signed in 1796 and says, "the Government of the United States of America is not, in any sense, founded on the Christian religion".
Going back to Madison, he said it best:
If you allow the state to say "there is a God" the state gains the right to say "and it is the God of this specific group".
And to throw it in since he's a Hoosier, below is what the state constitution says which makes the rest moot for Hoosiers.
Section 3. No law shall, in any case whatever, control the free exercise and enjoyment of religious opinions, or interfere with the rights of conscience. Section 4. No preference shall be given, by law, to any creed, religious society, or mode of worship; and no person shall be compelled to attend, erect, or support, any place of worship, or to maintain any ministry, against his consent.(History: As Amended November 6, 1984).Section 5. No religious test shall be required, as a qualification for any office of trust or profit.Section 6. No money shall be drawn from the treasury, for the benefit of any religious or theological institution.
Clearly, no one has the power to say, "members of X cannot be elected, or cannot vote". As a result, religion will never, ever, be eliminated as one might suspect. Look at the Supreme Court, all claim a religion. Have we had a known atheist in the White House?