I live in Colorado too, and can't ever remember anything that rude happening around me. The worst that I have seen is that race-type roadie indifference to anyone that does not average over 26 mph on the flats, and the wide-eyed stare at my old mountain bike (no suspension at all) from technical mountain bike types on the trails. You know, the polite, but wide-eyed "you are riding THAT?! HERE?! ARE YOU FREAKING NUTS?!" look?
Those guys that laughed at you suck. I agree with others that you should not let it bother you. I could do that if it were just me they were talking about, but I have more problems looking the other way when it happens to a freind of mine. Knowing my track-record with such things, I probably would have made eye contact, and replied with some sort of self-deprecating joke that also makes them look like school-boy idiots, or a direct "grow up" statement . Adding tension to a situation with an idiot is not a good idea, though.
Ranting online seems like a good way to "do something about it", without making the situation worse, though...