A former friend from high-school has a similiar belief system. He kept talking about getting jumped by punks on the astral plane, building better shielding and altering the root level of reality. He too used the White Wolf games in his beliefs, if only to help explain things. There were lots of funny things that came out of his lunacy.
For instance:
Once when his first girlfriend (who he lated stalked and insisted made him impure because he lost his virginity to her) was at his house just hanging out he got a really intense look. He told her to be quiet, layed his hands upon her head and when he removed them nodded and looked quite satisfied. “I just removed the tracers that the oblivion wizards placed on you. They’ve been trying to find me to corrupt me. Ironically that was the plot of a video game I just rented.”
After we helped him move out from a place he was renting he mentioned that he was going to curse the place “Because I can do such things.” No one decided to correct him.
His metaphysics involved a vague, and bad, computer metaphor as well as some nebulous “energy” that was supposed to get everything done. It sounded remarkably like the sort of paradigms you get from bad Mage players.
Now the thing is none of this was enough to break the friendship. Sure he was a nut job but no one is totally sane. It was only when he started being a total ass to another of my friends and making scenes in public to belittle the other friend that my friends and I decided we were sick of him.
So the moral of the story is that yes they can believe that but it doesn’t mean they are going to be asses or bad friends. One added bonus of people who believe in their own supernatural abilities is that if you piss them off there is a pretty good chance they’ll just try cursing you instead of doing anything productive.