Well, happily, you seem to have conceded the point that the original intent of the 14th Amendment was not intended to incorporate the "establishment clause" of the First Amendment. You get big points for that.
But, the misunderstanding from my perch is yours and a lot of others who conflate indidual inalienable rights granted by the Creator, or natural rights for the less relgiously inclined.
In other words, the "establishment clause" was a constraint on the federal government and the federal government alone while the inalienable rights to speech and the written word are without a doubt are incorporated by the 14th Amendment.
Let's say the 14th DOES incorporate the 1st against the states--but the 1st Amendment was never intended to protect commercial speech, for instance--but everyone on the Court today recognizes that the 1st Amendment protects commerical speech, and that includes Scalia and Thomas. Heck, for that matter, the 1st Amendment was never intended to protect political speech that was critical of the Administration--see, for instance, the Alien and Sedition Act which was drafted by many of the same folks which drafted the Constitution and the Bill of Rights. I think the most accurate "originalist" glint on the 1st Amendment was that it intended to forbid "prior restraint" by the government. We can't stop you from saying it, but once you say it, you can still be put in hot water.
I doubt seriously whether the authors of the 14th Amendment intended to "incorporate" the establishment clause against the states, but it's really a non-issue. I don't think even the largest "originalist" in the world would argue that the 1st Amendment shouldn't apply against the States. I consider Thomas to be the biggest "original intent" Justice on the Court, and I've NEVER seen an opinion of his which claims that the establishment clause shouldn't apply against the States. Maybe I'm wrong.
I'm concerned with a lot of the language floating around today to describe judges because there's simply no such thing as an "originalist" or "textualist." They can't exist in today's world; they'd never become judges.
So essentially what I'm saying is that from where I sit, the "original intent" of the Founders is a red herring, clung to or villified by any judge, just depending on whether the original intent supports his position or not. If the "original intent" supports his argument, you bet he'll cite it or quote it or whatever. If it appears that it doesn't, it's pushed to the corner and maybe mumbled about in the opinion and then glossed over to make room for the expanded version of events. The expansion of rights is not a bad thing, as I see it, especially when it comes to preventing government oppression in the form of religious persecution.