It's difficult to comment without knowing more. Was the guest a professional/semi-pro who for some reason had a bad night? That would be unusual, but it happens, especially if they like a drink!

If it was an inexperienced amateur who somehow was given a gig, then it seems to be a misjudgement on the part of the organiser. But doing a gig is a lot more pressurised than a floorspot, and it may be that someone who had appeared to be sufficiently competent just fell apart on the night.

If the performance was fine but the guest's music wasn't to the audience's taste, well "folk" is a broad church and we can't be expected to like everything. However the organiser should have a better understanding of the tastes of his or her audience.