[Fourth in a series]
You're right, that the real problem with faith, is the required abandonment of objective reality. It sets you on a path, where you're not really in control any more of where you end up. Since you're no longer accepting feedback from the world to calibrate your beliefs, you can be led (by a sufficiently motivated manipulator) almost anywhere.
You say that it's "extremism", not religion, that I'm objecting to. And you're right, to find examples of religion that are not extreme. But I think you really underestimate the connection between religion and extremism. The reality is that religion requires faith, which sets you up for being unable to distinguish between extremism, and moderate belief.
For a significant fraction of the world's religious believers, being a "moderate" believer actually requires a bit of hypocrisy. For example, one might simultaneously claim that the Christian Bible "is the literal Word of God", while at the same time, in practice, focusing almost exclusively on the New Testament and "just coincidentally" ignoring the many tales of God's brutality in the Old Testament.
Ron, you mention Buddhism and Quakerism, but I don't see how one can thread the needle of being pro-religion (in general) while simultaneously anti-extremism. Much of a serious attack against extremism would be seen, by religious believers, as an attack against their religion. Oh, sure, everyone would pay lip service to "being tolerant", and they would never recognize themselves as extremists. But then you would come to criticize things that are important to them, and I don't think they would appreciate the fine distinction you are trying to make between extremism and religion.
As for Karen Armstrong's books, my objection is that she doesn't seem interested in Truth. But I remain (thus far) convinced that much of the benefit of religion doesn't come to the believers, unless they actually believe. (At least, the part separate from the benefits of belonging to a community with shared culture and rituals.)
That's the fundamental conflict that I see. If you (and Armstrong) are just saying, "let's keep this mythology for cultural reasons", then that argument should work just as well for fiction. I'm certainly not against childhood traditions like Halloween and (secular!) Christmas.
But that isn't enough for (most) religions. They can't just be Harry Potter or Lord of the Rings. There's something more ... there's a claim to Truth, but achievable only via faith, not through observation. And it seems to me that once you head down that path, you're no longer capable of controlling where you end up.