Should there be religious freedom in the world or may religion be forced on people by majority?
That's one of the fundamental themes of modern history.
Historically, religion has typically been a group matter. It wasn't individuals that had a particular religion so much as it was entire cities, nations or peoples. (And in some cases, ideally at least, the whole planet.)
In the Bible, the Hebrews had their Hebrew religion which was pretty much inseparable from their ethnicity. Greek cities had their patron deities, such as Athens' Athena. Mohammed preached what he said was God's favored social order. Confucianism is all about organizing society.
As late as early modern times, Europeans had and often enforced, state religions. Entire peoples were (nominally at least) either Catholic or Protestant, as a community and not as individuals. (Usually it was the king or prince that chose a faith, typically doing so for political reasons, and then ordered his police to enforce his choice on everyone else.) Established churches still vestigially exist today in some European countries, such as the Church of England, the Lutherans in parts of Scandinavia, or the Catholics in southern Europe.
In the Islamic world, the equivalent of established churches oftentimes are far from vestigial. It's still a death-penalty offense in some places to convert to a different religion or even to blaspheme the established one.
Gradually European intellectuals started to question the equation of religious faith with an entire community. What really drove that change was the Thirty Years War that dominated the first half of the 1600's. The war was really about political power for or against the Hapsburgs, but both sides justified their actions on the street to their people in terms of defending true religion: the Hapsburgs pro-Catholic, the anti-Hapsburgs pro-Protestant. (Which put France in the odd position of being a Catholic country leading the Protestant side.)
So by 1700, Europeans in general were growing far more cynical about the whole thing. Their intellectuals were increasingly opposed to and critical of established churches and church privileges. Coming out of the 'wars of religion', what Europeans feared most of all was what they called "enthusiasm". The word has positive connotations today, but in the 1600's it was more-or-less synonymous with what we call 'fanaticism'. The alternative was to be cool and rational. That was in keeping with the scientific revolution and it pushed the movement towards Deism. The 'age of reason' dawned.
It was the new United States in the late 1700's that took the then-radical step of putting the new ideas into actual practice. The new nation's constituion recognized religion as a matter of individual conscience. The establishment of religious faith by the state was expressly forbidden. In the 19'th century, most of Europe followed that course as well, in practice if not in form (leaving the remaining state churches kind of vestigial and meaningless). It became perfectly ok to be what the British called a "dissenter", somebody who doesn't personally adhere to the state church.
The big fundamental change in all this is that religion went from being a
collective matter (as it still is for most Muslims) to being an
individual matter. That change in turn has fundamentally changed religion's role in people's lives and how it's practiced. And the community, society as a whole, has emerged from the change in a newly
secularized and at times even a-religious form.
We are still feeling the reverberating echoes of those fairly recent (last few centuries) changes. Exactly how all this will play out in practice is still being strongly contested.
In the United States, religion is still welcomed on the individual level. The problem then becomes what happens when individual religious believers vote their consciences in such a way as to enact their moral views into law. If they get away with doing it, isn't that establishment of their faith by stealth? But if religiously-inspired morality is ruled out a-priori, while non-religious arguments for moral legislation are privileged, then isn't that effectively the establishment of irreligion as society's guiding force? That surely wasn't the founder's intention either.
In Europe, the battles over religion have historically been a lot bloodier, leading to a much stronger reaction against churches in particular and against religiosity in general. Europeans, especially their intellectuals, are far more anti-clerical and anti-religious than most Americans. In Europe, the 'death of God' is welcomed and celebrated as a liberation. Which has left the ground cleared for a host of new ostensibly-secular quasi-religions, claiming the vacated turf and trying once again to enlist entire communities into a single and militant new faith -- whether Naziism or Marxism. Just as their experience with established faith was deeper and more violent than America's, their reaction against it, their experience with the aftermath of abandoning their ancestral communal religiosity, has tended to be more turbulent and 'enthusiastic' as well.
And now these historical forces are spreading around the entire planet, driven by instant digital communications, world-wide transportation and economic globalization.
It's a big part of what's gotten the Islamic world so terribly agitated. To them, religious individualism and state secularism are perceived as challenges to Islam's fundamental essence.
