>>280576059
I'm sure it was at some point, and breaking taboos by making his major heroes christians was probably part of the fun for people like Nagai, but the extent to which WMT and shoujo portrayed religion leads me to think "taboo" was a bit of an exaggeration by the 70s. Stuff like Flanders no Inu goes beyond "documentary freedom" as religion becomes part of the core narrative and themes. The ending is pretty legendary for that.
https://www.youtube.com/watch?v=NxsXErQsf8I
I can give you that Takahata scrubbed religion out of Heidi though. It was probably for the best too.