Brian over at Kairos recently posted about a run-in with what he terms a "McBuddhist".
In point of fact, yes, the Church claims universal moral authority. That is why she calls herself Universal. Christians hold that Christianity is true, Boomer-grade solipsism notwithstanding.
But more to the point, Christendom is Christian. It doesn't take a genius to see why living within Christian society while denying Christian moral authority instantly nullifies one's moral lecturing.
Expanding the First Amendment beyond the Christian denominations was a mistake.
The 1A was written to keep Christian denominations who are in 90% theological agreement from killing each other over what the sacraments mean. Anyone who thinks it suffices to keep adherents of alien creeds from over the horizon at peace is contradicted by logic and history.
There's also quite a bit of interesting commentary.