I can certainly understand why Karl Marx thought that religion was the opiate of the masses. History is replete with examples of how religion was used by rulers to deflect and deligitmize rebellion.
However, when you look at actual rebellions, religion is usually an important factor. Below is an imcomplete list of rebellions that were guided by relgious movements.
Palm Sunday and Easter
Such was the quality of Christ’s ministry that people from miles around gathered to welcome Christ to Jerusalem and spread palms in his path. Such was the quality of the Sermon on the Mount that the Roman occupation took fright and crucifed him a week later to put and end to the insurrection. Indeed, they knew not what they did.
And it is not hard to see why Wycliffe’s bible had such a radical effect upon the peasants who read it. Imagine being intimidated all your live by your local priest, and seeing the bishop from afar living in his palace surrounded by finery. Then imagine reading the Book Of Acts for the first time:
44 And all that believed were together, and had all things common.
45 They sold possessions and chattel [They sold possessions and substances, or goods], and parted those things to all men, as it was need to each.
46 And each day they dwelled stably with one will in the temple, and brake bread about houses, and took meat with full out joy and simpleness of heart, [Forsooth day by day they lasting together in the temple, and breaking bread about houses, took meat with gladness and simpleness of heart,]
47 and praised together God, and had grace to all the folk [praising together God, and having grace to all the people]. And the Lord increased them that were made safe, each day into the same thing.
The contrast between those words that the wealth of the medieval church must have been staggering. You can’t read the Book of Acts without realizing that Christianity preaches equality and any political doctrine that teaches otherwise is contrary to Christianity. It must have been an intoxicating experience to the English peasant.
German Peasant’s Rebellion
143 years later, the peasants of Germany had precisely the same reaction to the New Testament. When given the chance to read the word of God for themselves, they realized it bore little resemblance to the teachings of the medieval church. Martin Luther and other leaders of the Reformation turned against them, but the cat was out of the bag. Once people could read the word of God for themselves, the old obediance would never entirely return.
The Dutch Revolt
You just cannot separate the Dutch war for independence with the Dutch Reformation. The two are so intertwined as they cannot be separated. The Dutch revolt was driven and shaped by Calvinism.
The Indian Independence movement
While Ghandi was careful to build a multi-reglious movement, he completely embraced Hindu ascetism as part of his message of non-violence. Religous commitment on the part of his followers, of whatever religion, gave them the strength to maintain non-violent discipline in the face of violent provocation.
The American Civil Rights movement
It is not a coincidence that it was led by black ministers. It is not simply that the black church was the only institution that completely belonged to the black community. The Gospel of Jesus Christ that enabled activists to maintain non-violent discipline in the face of violence.
The Philppine Snap Election
Corazon Aquino’s devout Catholicism sustained her in the aftermath of her husband’s murder and enabled her to overthrow Marcos without violence.
Although the intellectuals who led the Committee for Workers (Polish acronym KOR) were secular Jews, the Solidarity movement itself was led by devout Catholics like Lech Walensa.