For one thing, this is in keeping with the Appendix N style of literature that my own worlds favor. Books like "The Dragon and the George" and "Three Hearts and Three Lions" managed to successfully blend stories of the fantastic with the Gospel Truth, so why not my own table?
Some say it raises difficult questions, but I say that it doesn't have to. Don't overthink things. You're a holy warrior in a fantasy land that has some connection to medieval Europe, and you serve a church that uses the cross and Christian iconography. You fight the spawn of the devil in all its various forms. Call them demons, call them children of Chaos, call them Al, it doesn't really matter.
The important thing is that you are a holy warrior fighting evil. If that means you utilize a fantasy version of Christianity that isn't strictly accurate, so be it. We use a fantasy version economics and biology that isn't strictly accurate, too. They are close enough for tabletop, and so long as your warrior can adhere to a Christian worldview that's close enough for the tabletop, so be it.
|Angels in the dungeon|
If my DM style makes a player uncomfortable, then they have the same option as they do when my culinary style makes them uncomfortable: push away form the table and find another DM or cook. No hard feelings.