I don't think it's the style that's the only problem.
I have a bunch of friends who enjoy extreme metal, much like I do, and that's the one bond we have. However, I have other interests, too, and I'm not keen on discussing it all the time. "I think X band is death/black metal and not just death metal." "I...don't care." I like nature and going out to pubs and things like that, and I have an interest in rugby league, so these things are something I'd enjoy talking about sometimes.
phocas, you're right that having a group where one or two people are dominating gets tiring and it makes me not want to be in that group at all.