p.s. I confess that I can, in part, understand how the anti-religion mentality of the French radicals had arisen, and why it made sense to them.
Nowadays, there is a lot of talk about “Crusades and Inquisitions”, but neither of these were on the minds of the French thinkers of the time. Instead, you had:
–the French Wars of Religion, essentially a civil war between Catholics and Protestants (which lasted, on and off, for approximately 35 years, from 1562 to 1598)
–the Church-State alliance of the Old Regime, and the Divine Right of Kings, whereby social injustice (the dominance of the poor by the rich) was enshrined and maintained through a political and ideological alliance between the monarchy and the clergy
The philosophers of the French Enlightenment reacted against the two “evils” mentioned above. It’s what Voltaire meant when he cried “Crush the Infamy” and what Diderot meant when, in a presumed moment of vehemence and pique, he wrote, “Men will never be free until the last king is strangled with the entrails of the last priest.”
Ironically, this fighting between Catholics and Protestants – no less destructive and divisive, in its way, than the American Civil War – and this church-state alliance, which had become identified with the Old Regime, is what largely “inspired” such a strong reaction from the Enlightenment philosophes, and then an even more radicalized reaction during the Reign of Terror.
In a way, though, I can well understand the vehemence of a Voltaire and a Diderot, given that the latter was locked up in the Bastille because his writings were deemed subversive to both state and religion. In that sense, there was a climate of much greater “cultural unrest” in France than there was in the American colonies. It probably helps explain the almost militant secularism that exists in France, even today.