Got an opinion on the theological difference between "being saved" and "demon possession"?

I think being “born again” is a precondition for being saved, because being saved requires a conscious choice; however, the phrase “born again” has a lot of connotations that I don’t care for in 21st century American Christian practice, and so I prefer not to use it.

I think God accepts everyone who accepts God, and I do not believe that a God capable of forgiving everything else will not forgive ignorance. I believe that Hell is the state of being willfully apart from God, and that God does not damn people to Hell, but that people damn themselves to Hell – and that they can un-damn themselves at any time they want.

From your Wikipedia link: “Spiritual possession is when ghosts (demons, devils, negative energies etc.) control the mind (emotions, thoughts) and intellect (decision making ability) of a person. As a result, they also control the person’s actions.”

This is qualitatively different from being saved, or even from being inspired by the Holy Spirit; the greatest gift God gave us is free will, and He does not take that away no matter what. Without the freedom to do evil, the choice to do good is meaningless, and so God, Who prefers that we do good, but Who loves us enough to give us free will, does not take away that choice, and does not judge us for our actions when the inability to choose good is taken away from us.

As a result, demonic possession is qualitatively different: if the possessing entity takes away the ability to do good or prevents the possessed person from being able to discern what is good and evil, then the inability to do anything but evil and the conscious choice to do something perceived as good when it is actually evil are both spiritually meaningless. It’s the choice to do evil when there is a possibility of doing good that matters.