I think these reactions were partially due to the idea that religious belief/faith should be the default in a child. I disagree, and wonder, "Why?"
Billions of people believe that their children must follow their religion to go to heaven and avoid going elsewhere.
I'm an atheist myself but keep quiet around the children, mainly because my wife want to raise them as X. Religion provides a sense of belonging to a group (with the side-effect that people of other religions are NOT part of the group). People tend to marry other people of the same religion, and I mildly prefer that my children marry people of the same religion/ethnic group as our family's. That's another benefit of my children being at least nominally (like their dad) of religion X. Since I cannot honestly proselytize for any religion, I will let my wife take the lead.
