...Ordinary people, moreover, have come to use “religion” in contexts having nothing to do with either gods or ineffable forces. They say that Americans make a religion of their Constitution, and that for some people baseball is a religion. These latter uses of “religion” are only metaphorical, to be sure, but they seem parasitic not on beliefs about God but rather on deep commitments more generally.
So the phrase “religious atheism,” however surprising, is not an oxymoron; religion is not restricted to theism just as a matter of what words mean. But the phrase might still be thought confusing. Would it not be better, for the sake of clarity, to reserve “religion” for theism and then to say that Einstein, Shelley, and the others are “sensitive” or “spiritual” atheists? But on a second look, expanding the territory of religion improves clarity by making plain the importance of what is shared across that territory.
No word on what this would mean for any readers who are "spiritual but not religious." I think it means they're religious again. Worth reading--kind of an orthogonal take on the usual boundary disputes about what it means to be a believer.