I've said it before, I'll say it again: If I thought that religion was false but beneficial, or even just a harmless diversion, then I wouldn't object to it as strenuously as I do, and I certainly wouldn't spend as much time writing about it as I do. I argue against religion because I think it's dangerous, because I think it does more harm than good, and because I think that when people give it up, humanity will be better off. As far as I'm concerned, atheism isn't an end in itself but a means to an end, and that end is the creation of a freer, more peaceful, more enlightened world.
I don't mean that religion has only bad consequences. People's religious beliefs can bring them together in community and inspire them to acts of charity; but people's religious beliefs also motivate and promote ignorance, hatred, prejudice, xenophobia, violence, terrorism, and holy war. I'm confident that if we give up religion, we can get rid of these evils without losing anything good. There are perfectly good secular, humanist reasons for forming communities, engaging in charity, and treating each other with compassion and dignity, and I happen to believe that people would do these things whether or not they believed in a god.
First of all, let's point this out: we largely have no idea what would happen if everyone on earth were to "give up religion" in all its guises, from monotheism to animism. Nothing of the sort has ever occurred before, obviously. Breezily claiming that we would all be "better off" is basically a meaningless statement of the "colorless green ideas sleep furiously" variety—grammatically and syntactically correct, but lacking any real-world referent. The ripple effect from such a profound alteration of basic human psychology would be unpredictable, to put it mildly.
And we are talking about psychology here, not rationality. Religion is an outgrowth of humanity's communal impulses, not an imposition from the outside. People didn't decide, as rational agents, to band together and submerge their individuality in the group because they heard one clever person tell a story about a man in the sky who wanted them to do that; that's completely ass-backwards. People naturally form groups. The stories they tell themselves about their groups are what we call myths. These myths can be more or less grandiose, but they all help people make sense of their experience—"sense", as in, symmetry, cohesion. Humans, like any other animal, have no inherent purpose but to exist and reproduce. Seeking truth for its own sake through science and rationality is just one of the supplementary purposes we've come up with, and if that truth is disheartening and disorienting, people aren't being "unreasonable" to reject it in favor of myths. And the idea that humans are destined or obligated to recognize their essential kinship and work together to maximize the reach of a certain set of abstract values is itself a myth. A story that orders experience in a pleasing way so that people like Adam won't suffer a crippling existential crisis.
Ignorance, hatred, prejudice, violence, xenophobia, war—I happen to believe that people would do these things whether or not they believed in a god.