So is there a roadie nickname for mountain biking?
I'll bet there is and I bet on a roadie forum somewhere there's someone moaning about it right now. It's just a nickname, don't worry about it.
Dunno what the problem is with expecting a reciprocated hello if "it's all cycling". Yes I say hi/wave if I see another cyclist, no I don't wave hello to everyone in the street but if I'm out in the countryside I tend to greet anyone I meet walker/biker/horsey. If you're in a minority/gang/clique/niche it's nice to say hi, and in the street we are certainly a minority. None bikeys at work don't get it either "I don't wave to all the other drivers".
mind you I don't get all P'd Off about it if they don't reciprocate.