that's their right in a religiously pluralistic republic

Rights end when deliberate undermining of civilization begins.

While Christianity was unfortunately not explicitly in the founding documents it is all over the writings implicitly. Do you think John Adams meant Aztecs when he wrote "moral and religious people"? Even if you can make the very tenuous argument that Christianity shouldn't be acknowledged at the federal level there is absolutely nothing that would come close to providing an interpretation of "freedom of religion" that banned Christian prayer before State sponsored public events, nativity scenes, crosses on public buildings, etc.

The idea that "religious liberty" would extend to satanic temples or muslim calls to prayer is intentional subversion.