It's not clear to me that sunday school systematically makes kids' lives any better, and the epistemic danger seems real enough.

For instance, the guilt-trip nature of the doctrine of "original sin" strikes me as a clear harm when inflicted upon children, who do not have the intellectual resources to receive it critically.

It's one thing to tolerate people who choose to have certain beliefs. It's another, more difficult, to tolerate people who actively foist these beliefs onto the more vulnerable.