There're a few things to consider here:
Offensive content should be flagged to the moderators.
If it's obviously offensive or you, yourself find it offensive then please flag it as such. This is the flag option to select:
Things I would flag as this is explicitly saying that a religion is fictional. Subtly implying it as such is not for instance offensive to me, but I would 100% accept a flag from someone saying they were offended by such implications. I'd much rather listen to the community speaking up about it than impose what I thought the community wanted.
The other side of the coin is that, answers that use a non-fiction source are simply poor answers in some case. First though, let's be clear on which meaning of fiction I'm refering to:
Literature in the form of prose, especially novels, that describes imaginary events and people.
synonyms: novels, stories, creative writing, imaginative writing, works of the imagination, prose literature, narration, story telling
something that is invented or untrue.
"they were supposed to be keeping up the fiction that they were happily married"
synonyms: fabrication, invention, lies, fibs, concoction, untruth, falsehood, fantasy, fancy, illusion, sham, nonsense;
I would say the majority of religious texts may come under the category of Stories, or Narration implying they are invented or untrue is likely not the intention of the original author. The accepted answer on the related meta post uses the idea of whether it would be in the sci-fi or fantasy section of a book shop. While it's not an exhaustive criterion, it's probably easier than trying to understand the intention of the original author in some cases.
By either metric most answers that treat religious texts (regardless whether they're Judeo-Christian, Islamic, Hindu, Shinto, Buddhist, Druidic, Pagan, Ancient Roman, Ancient Greek etc....) are simply not providing a good answer, and I'd expect them to get the same response as using Time Cube as a scientific source on Physics.SE - it's just not on topic. Downvote and move on.
There is one exception though. If a question is asking for the inspiration behind a work of fiction, answers citing religious texts should be considered valid.