In reality, of course, demons do not exist. They are simply used, like their "good" counterparts, angels, to "explain" certain phenomena. In modern western society, the number of unexplained phenomena is much lower than in more primitive times and places, which, thankfully dilutes the harm of such beliefs. For example, we now (mostly) understand diseases such as epilepsy and schizophrenia and realise they can be better treated by doctors than priests. The danger arises when someone comes across an unexplained phenomenon, or one they are unfamiliar with - such as sleep paralysis, the likely cause of dido's experiences - and due to religious indoctrination, assumes demons to be the cause. Sometimes that doesn't matter too much, as there is an imaginary cure to go with the imaginary cause of the imaginary affliction. The right incantation to the right deity vanquishes the demons. Sometimes, however, the affects of this absurd belief are not so neutral. People may live in fear for years due to something as mundane as a clanking water pipe, because they have been conditioned to believe they are engaged in a spiritual war with invisible enemies. Or worse, they may avoid treatment for a real medical condition because they - and their loved ones - believe it to be a demon attack. Aren't we advanced enough to throw of the shackles of primitive superstition? There are no invisible people waging war for our souls, no spirits trapped in old houses, no incubi or succubi wanting to breed with us. There is only reality - actual, hard, cold, measurable, understandable, beautiful reality.
Amen!
j