Here's a random thought: If demonic possession is a thing, why isn't angelic possession?
Think about it, if religious hysterics are real -- and they are -- then why don't these same hyper religious people ever convince themselves that they've been possessed by an angel? Why is it always a demon that possesses them? Is it because they enjoy putting on the show of spitting, swearing, vomiting, urinating and defecating on themselves so they can revel in the shock and attention it brings them? How would an angelic possession even work? Would they become extremely polite, helpful, caring and calm? That wouldn't make for much of a horror movie.
Has anyone ever claimed an angelic possession? I 'm not aware of it so it's probably an idea that's long past due.