I remember a news story about a couple who got booked onto a gay cruise, the only straight customers on the boat as I recall. Nothing particularly wrong, but awkward...! Ah, here it is: Heterosexual couple booked on a gay cruise sues cruise line | Gadling.com Excerpting...
Same scenario some GLBTQ people feel surrounded by 'straight people' - you don't see why they might prefer a dive club with other GLBTQ divers, but you can understand why the straight couple on the cruise felt 'awkward'....
As others have said, we've got all different kinds of divers, and there are groups for just about all of them. Why? Life has enough dealing with other peoples crap....diving shouldn't....so people seek out people similar to themselves (whether it be based on gender - ladies only clubs, sexual orientation, or dive philosophy (diving with others who share your diving philosophy/beliefs can avoid discussions or hassles maybe you just don't want to have). Do I dive with lots of other people? Sure. As a GUE trained diver though, sometimes I just want to dive with other similar divers - nothing wrong with that. Diving is supposed to be fun and enjoyable - if it isn't, then you're either not doing it right, or with the right people (no DIR pun intended).
Just my two cents while I kill some time as I nurse a sick wife....hopefully better before our trip to North Carolina. Cheers!