Some rules I live by...
1) Don't assume everyone with an expensive bike/ gear is a racer. Most of them aren't.
2) Don't assume that everyone on an older/ beater type bike is an obstacle. Some of them will drop you like a bad blind date.
3) Don't be a snob to anyone on the road. We all ride together, let's all be civil.
I try to be friendly to everyone. I know some riders get way into thier training and don't acknowledge others on the road. That's fine as long as it's not accompanied by snobbish attitude.
I'm saying, if you fit into rule #1, and violate rules 2 & 3, you might get embarassed.
One guy in the club I ride with is a snob. He has a pretty CF bike w/ full Dura-Ace. Everytime I see him he has some shiny new upgrade, and asks if I've upgraded anything on my bike "yet". I usually respond, "just the motor". Which is the ONLY thing this guy hasn't upgraded. He has made a few rude comments about my weight.
He's all of 5'-3", probably under 150#. His bike probably weighs all of 16 pounds with the water bottles. I weigh close to double what he does. My bike weighs 50% more than his.
Yeah, when I get the opportunity to drop this particular guy, on a bridge especially, I'll do it. With great pleasure. He hasn't quite learned yet, but he IS getting better.
There are a lot of guys JUST LIKE HIM, that ride in our area.