I wouldn't call it elitism necessarily. It's an odd situation. And, it's kind of confusing at times. You are willing to perform publicly in a spontaneous setting, and you have to have some rules to keep the majority of the people happy. Often the problem is that some people don't recognize or respect the particular protocol for jamming. So what appears as elitism is an attempt to avoid conflict, by having defined parameters of types of music, insturmentation, number of individual performances, etc. Occasionally, you will encounter people who feel they are "too good" to mingle with the unwashed. Just ignore them, and find some people who enjoy one another. Chances are, that if you feel like they are elitists, everyone else does too.