I see everyone is being very gentle about this topic, so far. But I can't forget that there are still "Christian Nationalists" in the US (including in Congress), or that Iran and some other Muslim countries are boardering on theocracies.
In the United States, Christian Nationalism has been described as a "national renewal project that envisions a pure American body that is heterosexual, white, native-born, that speaks English as a first language, and that is thoroughly patriarchal." These are all (with the exception of the "white" and "English") thoroughly reflective of a biblical world-view, in much the same way that these same way the Islamic countries admire most of the same qualities.
I do not think it is possible to say that you want your nations laws (which apply to everyone) to also reflect your own particular religious beliefs, and not suppose, at the same time, that other religious beliefs must somehow therefore not be "true" enough.
More than 80 countries around the world favour a specific religion, either as an official, government-endorsed religion or by affording one religion preferential treatment over other faiths, according to a new Pew Research Center analysis of data covering 199 countries and territories around the world.
Islam is the most common government-endorsed faith, with 27 countries (including most in the Middle East-North Africa region) officially enshrining Islam as their state religion. By comparison, just 13 countries (including nine European nations) designate Christianity or a particular Christian denomination as their state religion.
But an additional 40 governments around the globe unofficially favor a particular religion, and in most cases the preferred faith is a branch of Christianity. Indeed, Christian churches receive preferential treatment in more countries – 28 – than any other unofficial but favored faith.
As the world (or at least the first world, western nations) become increasingly cosmopolitan and multi-cultural, I see this as problematic, and I also suggest that it demonstrates to some extent my comments in the OP, that "their creed, their religion's essential beliefs, are correct, while all others -- because they obviously don't agree with the central tenets of their sect, must be somehow lacking."
Now, some may argue that the reason for such favouritism is "social harmony," but I put it to you, how can it be called "harmonious" to reduce some (often large) component of your society as of lesser value?