Nowadays, at every level, right down to sessions and singarounds, there are all too often people who want to dictate how things should be run - even down to saying just what folk music is.

If you mean the organisers or with sessions and singarounds perhaps the regular group a) I don't see why thy shouldn't do this and b) I don't see anything new in this. I don't think I've been anywhere that hasn't had some limit somewhere along the lines as to what constitutes folk or is appropriate for their purposes at their event.

If you mean other people, I'm not sure that I've encountered it much in the real world but I am certainly aware of the topic at Mudcat.

In general, it seems to me that those with the more rigid what is folk ideas are happy enough for folk clubs, sessions etc. events each to run on their own terms. I do agree that some from the other side do not see each event having it's own limits as being reasonable though.