"It seems unavoidable that those doing the telling off think they are better than those being told off. "
You've said this before Richard - are you really claiming that solo singing is an indication that solo singers do so because they consider themselves "superior"?
"....on an event which, from your description, is the antithesis of what I mean by a session."
You are assuming that I am basing it on one event - I am not, nor are people arguing the case on a single event (or that it should specifically apply to sessions - it happens at guest paying clubs regularly), but a principle that if you come along to their club you will have to go cap-in-hand to ask permission to sing solo - and be faced with attitudes such as Richard's, that it is arrogance on your part to want to do so - the death knell of all solo performances, taken to its logical conclusion.
Our song tradition (unlike others) is not a choral one and the songs, with all their musical and textual complexities and subtlties lend themselves to individual interpretation, in most cases, demand it.
Surely the musical variations or uses of textual phrasing that singers use within the space of one single song make it this blindingly obvious.
By encouraging joining in, you are bulldozing all of these flat , making any individual interpretation a singer might choose to make utterly superfluous.
Jim Carroll