Interesting, even people who believe don't agree with each other.
People who dont believe disagree with each other too! Thats what makes us individuals! the information is downloaded from different sources in each one of us, it's a qerky little bunch of query's called personality!
As for ghost's being demons, well no one can say from one supernatural experience to the next exactly who or what they can be attributed to every single time!
There are many strange things out there in creation no one creature knows all the answers!