The problem guest, is when the rules of the session remain unspoken. There is a general belief that sessions in public spaces are, if not otherwise noted, open to one and all who wish to join in. That is why a few simple rules--like telling a newcomer what sort of session you are in and what the ground rules of participating are, would solve 99.8% of the resentment that is generated regarding elitism in sessions. The other .2% of the problem would be solved if people of a high level of technical ability who wanted to play with others like themselves either:

1) When in a public space, make clear that the session is like a concert performance for the benefit of the people present as an audience, and therefore, not open to anyone to join in, unless invited--just as it would be if they were on stage.

OR

2) Move the session to a private space.