I think this fails when you think of it on Bayesian grounds.
If we want to use the large number of intelligent religious people as evidence for the truth of religion, we need to show that P(intelligent believers|religion true) is greater than P(intelligent believers|religion false); that intelligent people are more likely to believe religion if it's true than if it's false.
But at most one religion can be true. Therefore, all other religions are false. But lots of people, many intelligent, believe both (for example) Christianity and Hinduism. If (for the sake of argument) we're wondering whether Christianity is true, then we cannot explain all the smart Hindus without admitting that people are just as likely to believe a false religion as a true one.
But if people are just as likely to believe a false religion as a true one, then lots of people believing a religion is no evidence that it is true.
There is an argument for shifting views towards general religious feelings, since that can't be disproven so easily. And I do shift my views a little in that direction. But remember that you can't double-shift. You have to shift them from the place they would be if no one believed in religion at all. IE, imagine a world where everyone was a scientific materialist, and imagine the credence you would give to this new hypothesis someone just dreamt up that the world was created by supernatural beings six thousand years ago. Then you can multiply that credence by whatever factor you want to use for the high level of belief people have in it. But the original credence is so vanishingly low that even the extra believers can't save it.
Also, re: Einstein and God. Richard Dawkins answers this better than I do. I suggest you read his work on the subject. The summary is that Einstein liked to use the word "God" as a metaphor for "physics", but wasn't a believer per se. Newton was, but he was also a believer in alchemy...
But I'd still like to thank you for bringing up this topic. You're using rationalist methods to support religion, which is exactly how all religious people should be doing it and which is something rationalists should take seriously. I'm a bit sad you're getting downvoted as much as you are, compared to some inane comments about how stupid all religious people must be that tend to be voted up. I predict most atheists will be overconfident in their rejection of religion, simply because most people are overconfident in any politically charged topic they feel strongly about. It's good to occasionally have to listen to intelligent rationalist arguments in favor or religion to avoid an echo chamber effect.
"But at most one religion can be true. Therefore, all other religions are false."
This is the single biggest reason why I can't understand why anyone believing any specific religion. Dawkin's classic response when asked "What if you're wrong?" is simply to repeat the question.
The question religious people should ask themselves is this: of all of the thousands of religions there have been in human history, what is the probability that you just happened to be born in a family who just happened to believe in what just happens to be the cor...
“Everyone complains of his memory, but nobody of his judgment." This maxim of La Rochefoucauld rings as true today as it did back in the XVIIth century. People tend overestimate their reasoning abilities even when this overconfidence has a direct monetary cost. For instance, multiple studies have shown that investors who are more confident of their ability to beat the market receive lower returns on their investments. This overconfidence penalty applies even to the supposed experts, such as fund managers.
So what an expert rationalist should do to avoid this overconfidence trap? The seeming answer is that we should rely less on our own reasoning and more on the “wisdom of the crowds”. To a certain extent this is already achieved by the society pressure to conform, which acts as an internal policeman in our minds. Yet those of us who deem themselves not very susceptible to such pressures (overconfidence, here we go again) might need to shift their views even further.
I invite you now to experiment on how this will work in practice. Quite a few of the recent posts and comments were speaking with derision about religion and the supernatural phenomena in general. Did the authors of these comments fully consider the fact that the existence of God is firmly believed by the majority? Or that this belief is not restricted to the uneducated but shared by many famous scientists, including Newton and Einstein? Would they be willing to shift their views to accommodate the chance that their own reasoning powers are insufficient to get the right answer?
Let the stone throwing begin.