So your THEORY goes, but what if demons are a corrupting force, impelling humanity to commit evil and experience negative emotions? What if they foster it? What if they nuture this as early as our childhoods? What if we all have encountered the Devil in multiple forms throughout our lifetimes and didn't realize it ... and most of the time he wore a human face?
The Bible calls the Devil... lord of the Earth... what if the whole Earth lies within his sphere of influence. And maybe only when our spirits return to God will we ever truly escape that sphere of influence rather than the chaos of physical reality.