Fiction is way too strong a word. Is law fiction? Is morality? Is the aesthetic of beauty? Is the concept of fairness? Those things are all the accumulation of people's ideas mediated through institutions, interpreters, and history. All scientific models and theories are like that. It may even be that time and causality are like that. Basically, those are anything that derives from a human understanding of the universe. Hardly bad company to be in.
We all have some sort of difference in our understanding of all those things, and all cultures have had differences. Just as with God. As long as you can do that and compromise with the guy next door who has a different view, you're participating in a democratic political system. There is nothing inherent in the concept of God, even in monotheistic exclusivity, that precludes that.
The problem we face now is a large sub-population who will not only refuse to compromise but will sabotage the working of democracy in order not to compromise. It doesn't matter what their reason is when they do that, they've taken themselves outside the system. Essentially, they're in rebellion, but it's a special kind of rebellion where they aren't sacrificing anything or putting themselves on the line, so they can keep it up forever because it costs them nothing.
On the other hand, it's non-violent (so far), so although it's disrupting solving national problems at least it isn't building up too high a body count.
