Possible reasons:-
The person involved was a teacher? I have experienced this syndrome myself and witnessed the same behaviour at other festivals. I have seen them revert to the techniques required when dealing with children when under stress. It hacks me off beyond belief.
Or
The artist(es) involved may have forgotten they are simply a big name in the folk world - try asking the average non folkie if they have heard of Martin Carthy. That kind of behaviour hacks me off beyond belief.

Before you all rip my head off, I am trying to suggest there are always 2 sides to an argument and usually mitigating circumstances. Most people have been involed in rows where what they have said previously has been quoted back supposedly verbatim, but the accused has no recollection of ever saying those words.

Don't let this kind of thing become an issue and an opportunity for gossip and chinese whispers. No-one needs it, especially people on a steep stage management learning curve. I have a mate who is a technical manager at a large Manchester venue and they could top and tail this little scuffle.