From Thomas Paine's Rights of Man
Throughout this work, various and numerous as the subjects are, which I have taken up and investigated, there is only a single paragraph upon religion, viz. "that every religion is good that teaches man to be good"(Common Sense and Other Writings, p250-251)
I have carefully avoided to enlarge upon the subject, because I am inclined to believe, that what is called the present ministry, wish to see contentions about religion kept up, to prevent the nation turning its attention to subjects of government. It is, as if they were to say, "Look that way, or any way, but this."
But as religion is very improperly made a political machine, and the reality of it is thereby destroyed, I will conclude this work with stating in what light religion appears to me.
If we suppose a large family of children, who, on any particular day, or particular circumstance, made it a custom to present to their parents some token of their affection and gratitude, each of them would make a different offering, and most probably in a different manner. Some would pay their congratulations in themes of verse and prose, by some little devises, as their genius dedicated, or according to what they thought would please; and, perhaps, the least of all, not able to do any of those things, would ramble into the garden, or the field, and gather what it thought the prettiest flower it could find, though, perhaps, it might be but a simple weed. The parent would be more gratified by such a variety, than if the whole of them had acted on a concerted plan, and each had made exactly the same offering. This would have the cold appearance of contrivance, or the harsh one of control. But of all unwelcome things, nothing could more afflict the parent than to know, that the whole of them had afterwards gotten together by the ears, boys and girls, fighting, scratching, reviling, and abusing each other about which was the best or the worst present.
Why may we not suppose, that the great Father of all is pleased with a variety of devotion; and that the greatest offence we can act, is that by which we seek to torment and render each other miserable? For my own part, I am fully satisfied that what I am now doing, with an endeavor to conciliate mankind, to render their condition happy, to unite nations that have hitherto been enemies, and to extirpate the horrid practice of war, and break the chains of slavery and oppression is acceptable in his sight, and being the best service I can perform, I act it chearfully.
I do not believe that any two men, on what are called doctrinal points, think alike who think at all. It is only those who have not thought that appear to agree.
Paine lays out a more elaborate argument against organized religion, specifically Christianity, and supportive of Deism, in The Age of Reason. I don't agree with many of his arguments in The Age of Reason, but as an indictment of some organized religious institutions, I think this is on target. In some ways, it seems that Paine was doing 200+ yrs ago, what some vocal atheists are doing today (Dawkins, etc.). That is, attacking the organization as if it were the same as the faith. That said, he has a point about the bickering, the belief in the superiority of one faith over another, and the unwanted and ill-advised mixture of politics and organized religion. It's as true today as it was when Paine wrote.