Auxiris,
I love your story about the folk club--folk music is supposed to have a universality about it, but instead, it brings out petty jealousies, territorialism, and becomes totally political--
I do not know how the law works in France, but here in the States it is possible sue for libel and slander--I would have gotten two great big constables and served papers on your Irish music person in Nancy, right in the middle of a the session, and perhaps right in the middle of a solo--and made a few calls to the local TV news people ahead of time to let them know what was happening--
After that, your "professional musicians" would, most likely, have raised no further objections to your activities--and of course, you would have let many people know about your club--
Of course, this sort of activity is not for everyone, but I believe that if something is important to you, you should not let others slight you--
I believe that you do have an audience for your music, furthermore, I believe that your detractors do too, or they wouldn't be giving you such a hard time--
By the way, my advice is not just an idle suggestion, I have made my entrance, brandishing legal papers, and accompanied by constables and the press, on several occasions when it became necessary--you do not always win, of course, but you do always get your message across--