When the ancient world was in its last throes, the ancient religions were overcome by Christianity. When Christian ideas succumbed in the 18th century to rationalist ideas, feudal society fought its death battle with the then revolutionary bourgeoisie. The ideas of religious liberty and freedom of conscience merely gave expression to the sway of free competition within the domain of knowledge.
Yeah, the Hindus and Buddhists are all, "Wut?"
"When Christian ideas succumbed in the 18th century to rationalist ideas" is a hoot because at least a good chunk of the Enlightenment thinkers considered themselves Christian.
"...feudal society fought its death battle with the then revolutionary bourgeoisie." Yeah, there was that extended Bourgeoisgeddon, to roughly the extent the ancient world had "death throes". Charlemagne thought he was just reforming Latin, and would have balked at the idea of these "death throes" that Marx is making up. It sounds as though Marx may have bought off on Edward Gibbon's biases, directly or not.
This is to say nothing of my contempt for Marx's view of private property. What a used car salesman. The Communist vanguard inevitably, invariably, with enough irony to float an Iowa-class battleship, becomes the aristocracy standing in the ashes of the bourgeoisie. The only thing to be done with this foolishness is to reject it, and haul it out with the kids for a cautionary tale about liars.