Here's Hadley Arkes on the matter.
...Widmar v. Vincent (1982) [ ] was a case in which the State of Missouri sought to block all public funding or patronage for religion. And so the University of Missouri at Kansas City, an instrument of the State, would not allow religious groups the use of rooms for worship and discussions. That policy was invoked to deny rooms to an Evangelical group named Cornerstone. When I used to teach this case, I brought out what was remarkable in it in this way: When the Supreme Court starts making serious mistakes in its rulings, and then those mistakes accumulate with layers of precedents, we reach a point when the Court can get something right only by accident. By the time Widmar had come along, the Court had remade its doctrine on the regulation of speech by backing into a stylish version of moral relativism. The signature line came from Justice John Harlan in Cohen v. California (1971): “One man’s vulgarity is another’s lyric.” Harlan’s novelty here was that he rediscovered the teachings of “logical positivism” that were all the rage when he was an undergraduate...Arkes points out that 'logical positivism' was a dead letter by 1971. But that didn't dampen Harlan's enthusiasm.
Anyhow, that had consequences.
...When the Court brought that teaching to bear on the problem of Evangelicals at the University of Missouri, it produced this ironic outcome: The Court would sustain a right on the part of the religious to have access to the rooms at a public university, but not because there was anything especially legitimate or salutary about religion in the life of a republic. Rather, the Christians couldn’t be ruled out because it was not legitimate any longer to make discriminations based on the “content” of the speech. The Christians couldn’t be barred for the same reason that the University could no longer rule out Leninists, Nazis, or Satanists....
(All of which now occupy faculty positions in most major US universities. Yes, that's "Badthink" but I'll think and say it anyway...)
Yes, this was stupid. In fact, it was monumentally stupid--and now we have "Christian warriors" convinced that Monumental Stupidity is......umhhhh........"good".
...for that was exactly the doctrine that David French was not only accepting but celebrating. The Widmar case had come to represent, for him, “viewpoint-neutral access to public facilities.” He went on to say, “Viewpoint neutrality is what we must defend. I want drag queens to come into a relation with Jesus Christ, but I am not going to usurp the Constitution to do this.”...Umnnnhhhh....wrong, Mr. French.
...French professes his reverence for the Declaration and the American Founding, but moral relativism could never be reconciled with a document that relied on the understanding of “self-evident” or necessary moral truths. Nor could French’s understanding of religion be reconciled with that of even Thomas Jefferson, who did not accept the divinity of Jesus. In his first inaugural address Jefferson said quite enough to detach himself—and us—from this new relativism on religion. He made the point that Americans, divided into different sects and churches, were neverthelessIn other places, Arkes expands on the above paragraph and argues that--in fact--SCOTUS historically ruled otherwise, as summarized here by Zmirak:
enlightened by a benign religion, professed, indeed, and practiced in various forms, yet all of them inculcating honesty, truth, temperance, gratitude, and the love of man; acknowledging and adoring an overruling Providence, which by all its dispensations proves that it delights in the happiness of man here and his greater happiness after....
The First Amendment, right up through the 1940s and 50s, was correctly read by courts as permitting the state to promote religion as a public good, and advance the natural law as conducive to the common good.
Well. It's clearly one or the other. Which choice REALLY "promotes the General Welfare"??