It's perfectly acceptable to see a jazz quartet doing their stuff with their heads buried in their music but I suppose it's the instruments that are talking. For a singer/musician it's a slighty different situation. An element of personal communication is required to successfully deliver a song, which you're not likely to accomplish through the top of your head.
I've no objection to seeing music stands, as long as they don't get in the way of the music, but I think the user has to be well disciplined to avoid staring at a piece he or she probably knows anyway but can't resist the lure of the "safety net".
To bbc I would say, if it gives you the confidence to play in public then go for it! Song Circles are the grass roots of music and should be supportive of anyone prepared to share their music with them. It's a different matter if you're paying to see an established performer who hasn't learned their act well enough, maybe then there's reason to gripe.