Actually, I probably don't agree that college-educated, white-collar peeps are a minority, or a majority, of metalheads. I haven't taken any polls or anything, but there are so many different types of metal, and so many different types of fan, that it's not easy to make any but the most broad generalizations. Who cares, anyway.
Case in point, found in a clicktrail started from the Wikipedia links in Dopp's previous post: Vedic metal! I had never heard of it until now, but in retrospect it should have been obvious. It's cool how adaptable metal is. Check out Singaporean Vedic metal band Rudra, and their sample MP3s.