Yeah I'm gonna have to go along and say that the attitudes in road cycling are substantially worse than they are in other enthusiast groups. I've been riding road for about 3 months and could rattle off a list of occasions when I've had other cyclists act inconsiderate (sucking my wheel for miles then trying to blow past me on a hill without a word of acknowledgement), rude (responding with nothing but blank stares when I show up at an open-to-all, broadly advertised group ride and introduce myself)), and hostile (making snide remarks as they pass me). I don't really mind the waving thing, like sometimes youre just too busy or tired to wave and that's fine. But I draw the line when people seem to go out of their way to act like a-holes, and I've never experienced the blatant a-holism that I have in the past three months of road biking.
I understand safety concerns. But those concerns are no excuse for acting like a jerk. If a new guy shows up for a ride, give him a chance! If he does something stupid, by all means let him know. But don't give him the cold shoulder and the attitude just because he's wearing a camelbak and has hairy legs.
I've really been turned off to the sport because of this. I love road riding, and will continue to do so. But my primary focus will remain with mountain biking. I'd much rather be a mtn biker who trains on the road sometimes, rather than vice-versa.
Im not trying to say all roadies are jerks- clearly the people on these forums are great, and I wish most of you guys were on the roads where I live And I have had a grand total of two positive experiences involving other roadies (both on the same day!), so I know there are civil people out there. But man, overall the attitude just sucks, and there seems to be this general agreement that "yeah, roadies are kind of jerks, but just stick with it and 'prove yourself' and they'll warm up to ya." Sorry, but a fraternity-esque hazing process of acceptance is not what I'm looking for in my recreational activities.
As a side note, what someone said about academics being insular jerks is spot-on too! I recently finished up my first (and last!) year in a PhD program in English. My advisor referred to non-academics as "civilians". The first time she did this I waited in vain for the laugh or smile that would indicate she was just horsing around. It never came. Wowzers.