I think I witnessed the incident mentioned, from nearby - was it on Monday, early afternoon?

Just to put it in context for others: yes it was a session in a hotel lounge open to all, but it was an area that was earmarked for sesssions during the Folk Week. It was the sort of session with quite a bit of solo or group performing that others were there to listen to. The bar opens out on to a hallway where anyone not too involved with the music can stand and watch, and on the other side of the hall there's another bar area that was only occupied by about four people at the time (one of them me - there were three of us playing melodeons together, which is enough to deter any casual mobile users).

Forgetting to switch off your mobile is understandable enough, but in that context it would seem to me like very bad manners to answer a call in the music session and continue one's conversation there. Anyone with a scrap of consideration would have apologised and hurried out of the room to take the call in one of the adjoining areas. If the person was not prepared to do this, then I think others were entitled to tell him how rude they found his behaviour.