What is the main idea of the given passage?

Directions: Read the following passage and answer the question.
When we examine the opinions of men, we find that nothing is more uncommon, than common sense; or, in other words, they lack judgment to discover plain truths, or to reject absurdities, and palpable contradictions. We have an example of this in Theology, a system revered in all countries by a great number of men; an object regarded by them as most important, and indispensable to happiness.  An examination of the principles upon which this pretended system is founded, forces us to acknowledge, that these principles are only suppositions, imagined by ignorance, propagated by enthusiasm or knavery, adopted by timid credulity, preserved by custom which never reasons, and revered solely because it is not understood.
In a word, whoever uses common sense upon religious opinions, and will bestow on this inquiry the attention that is commonly given to most subjects, will easily perceive that religion is a mere castle in the air.  Theology is ignorance of natural causes; a tissue of fallacies and contradictions.  In every country, it presents romances void of probability, the hero of which is composed of impossible qualities.  His name, exciting fear in all minds, is only a vague word, to which, men affix ideas or qualities, which are either contradicted by facts, or inconsistence.
In all parts of our globe, fanatics have cut each other's throats, publicly burnt each other, committed without a scruple and even as a duty, the greatest crimes, and shed torrents of blood. What for? To strengthen, support, or propagate the impertinent conjectures of some enthusiasts, or to give validity to the cheats or impostors, in the name of a being, who exists only in their imagination, and who has made himself known only by the ravages, disputes, and follies, he has caused.
Savage and furious nations, perpetually at war, adore, under diverse names, some God, conformable to their ideas, that is to say, cruel, carnivorous, selfish, and blood-thirsty. We find, in all the religions, “a God of armies,” a “jealous God,” an “avenging God,” a "destroying God," a “God,” who is pleased with carnage, and whom his worshippers consider it a duty to serve. Lambs, bulls, children, men, and women, are sacrificed to him. Zealous servants of this barbarous God think themselves obliged even to offer up themselves as a sacrifice to him. Madmen may everywhere be seen, who, after meditating upon their terrible God, imagine that to please him they must inflict on themselves, the most exquisite torments. The gloomy ideas formed of the deity, far from consoling them, have every where disquieted their minds, and prejudiced follies destructive to happiness.
Thus, man has remained a slave without courage, fearing to reason, and unable to extricate himself from the labyrinth, in which he has been wandering.  He believes himself forced under the yoke of his gods, known to him only by the fabulous accounts given by his ministers, who, after binding each unhappy mortal in the chains of prejudice, remain his masters, or else abandon him defenseless to the absolute power of tyrants, no less terrible than the gods, of whom they are the representatives.