The IP is wrong. The only category of people who would be offended by the word "mythology" are fundamentalists who don't know what the word means. The 90+% of Christians who are not fundamentalists (and therefore don't care) and fundamentalists who know what the word means (and therefore know that it has no bearing on the story's factuality one way or the other) would have no reason to be offended by the category. Per WP:SLANG, we should be writing using professional, encyclopedic language; this applies both ways  we don't use the word "myth" the way people who are ignorant of its technical definition, and we don't avoid the word solely to avoid offending such people based on their choosing to misinterpret us.  (聖やや)