Note that even in Herbert's world, most members of the congregation setting up OC retracted their support for the Bible and/or got executed by their churches so

Note that even in Herbert's world, most members of the congregation setting up OC retracted their support for the Bible and/or got executed by their churches soon after coming back home. Universal adoption came centuries later. I think something similar does happen in the real world. Sitting on a fence does win you hate from both sides, yes. But take for example Poland, a deeply Catholic culture with quite a bunch of Islamic symbolism (e.g. traditional szabla being a crescent-shaped sword, unlike the cross-shaped of the rest of the Europe) and even a well integrated Muslim minority (stuck around since repelling the crusade in 1410).