I think he means that, even though Ghostbusters is not a documentary, ghosts could still hypothetically exist. Or something.

Anyway, I remember a book I read several years ago written by a preacher whose soon allegedly had a near-death experience and went to heaven. Then he went on to claim that his son never actually flatlined in his surgery, so that obviously meant his son was as holy and pure as the prophet Elijah who ascended while still alive. It was ridiculous and insulting, but it’s sold as nonfiction and the kid got to play himself in his movie biopic IIRC.