People are confusing three different things here. Elitism is where people are excluded because they aren't seen as up to the mark. There's a place for that, but not in public sessions.

And it's different from a sirtuation where people are unwelcome for olther reasons, maybe because they are strangers.

And both are completely different thing from a situation where a boundary is set on the type of music or whatever that is welcomed in a particular session.

"You're welcome to take part in our game of football - but just remember it's football we're playing, not cricket." Nothing in any way elitist about that.

As for the business of unaccompanied singing, that's the least elitist type of session you can have. It gets away from a situation where people who don't play an instrument are marginalised. Instruments are great for tunes, but there are very few people whose singing is really improved by musical accompaniment, and any number of singers whose songs get pretty well lost in the sound.