What you want is to make that belief a political litmus test,
So you assert. The assertion does not prove the fact. Prove it.
The Founders saw the effects of doing it (Establishing a religious doctrine that held any deviation to be heresy) and wanted none of it.
The Founders were Christian men who were convinced that no viable government could long endure without a sound moral foundation, and they thought its best foundation was to be found (as Adams put it) in the more general Christian principles. They were virtually unanimous in their opposition to Establishment Religion, which meant to them the elevation of one specific religious doctrine to a place of dominance over all other doctrines thereby rendering any deviation from that doctrine a heresy.
I thought that in my post #35 I made clear my opposition to the imposition of any form of heresy, but apparently you were so focused on your objective of confining heresy to a single target that you could not accept any deviation from your objective as being anything but objectionable to you.
I find no compelling reason why I must tailor my words and thoughts to your objectives.
You dedicated that post to arguing over the definition of heresy. There's nothing there I can find states what your political position is.