Well it's his book and all. This sort of thing, this is his are of study.

Between you and me I never believed in ghosts really until he proved to me they were real, but it's always better to be safe than sorry. On the off-chance they were real, y'know. Best to take precautions.

[It makes perfect sense to him. People always said ghosts and spirits and spooks weren't real, sure, but if they were what would be the harm in putting down salt or knocking on the doorframe when you enter a house, just to be doubly safe?]