But really, I admit that I have this deeply-rooted fear that demons and magic might be real. I mean, read some interviews with real-life exorcists...
As someone whom was an agnostic a hairs breadth from an atheist at the time of reading it, and one whom LOVED Memnoch the Devil, no. I was never concerned with it being true, at all, in the least, nada. Demons and Mages are for fairy tales, stories and games, not for real life. They're incredibly interesting stories and themes, touching on the archetypes of heroes and redemption that show up all the time in our histories fictions, and they play on symbolic representations of our own struggles in day to day life.
Symbolic, powerful, fascinating and entertaining in the fictional mediums they exist in, never once were they ever a story of real life.
I mean...it's from a gaming company
As for the evil bit, I take from Shakespeare and American Horror Story, "There are no devils in hell, they're all here," and "all (devils)monsters are people."