LLMs do very poorly at judging the truth of long-term myths. When something has been asserted confidently on the internet over a long enough period of time it becomes baked into the weights, regardless of truth.

I provided a source from a religious studies scholar on Christmas trees specifically (one of the most frequently-cited "pagan" traditions). If you can point me to something with similar provenance I'll read it, but I'm not going to waste time on LLM responses.