>>But we are not prepared to have some self-important pillock (or pillockless) tell us we are not good enough for them. It's not an exam. It's not a driving test.<<

Maybe not, but it is a judgement of you. Did you get an explanation why you were not good enough for them?
What people think of themselves, does not mean other people have to agree.

Normally, it boils down to the style of the performer not suiting the style of the club.

We alll know how so often people say that somebody is crap, but really mean "I don't like that style of singing or music or something like that"