When my now exgirlfriend discovered that I played D&D, among several other rpgs (one even MORE occult based...but it sucked) she was kind of freaked out...she told me that it was because it was intimidating, but never would ellaborate...I'm still not sure, but I know that she claimed to be devout in her religion...
I would also never tell my grandparents about playing D&D...but then again, I don't plan on telling them that I'm a deist or that I'm dating a Jewish girl any time soon...
Really, what it boils down to is "how absorbed do people become in the things that they do?" Most of the roleplayers I've met have been casual, and I'm pretty sure that that is the majority of them...unfortunately, those crazies who dress up as vampires and wander around quoting their respective games in the middle of airports DO exist, and give the rest of us kind of a bad rap...
After all, it IS man's typical reaction to generalize groups by the most easily seen examples...and those people certainly are that...