I must say that I do not remember any incidences of swearing/bad language in the folk clubs during the 60s and 70s. There were plenty of B words - bloody, bugger and bastard - but NEVER the f word and definitely not the c word. These were also verboten on the TV and radio until much later - probably into the 80s and 90s. And they caused very raised eyebrows when they first started appearing. I think the folk clubs reflected society as a whole when these words first started popping up in folk clubs. Even the folk comedians were very proper in this regard - it was the alternative comedians (the Ben Elton generation) that first made it more acceptable. Billy Connolly was one of the first to use this on TV, and it was the shock of his language that probably earned him the attention he got. Apart from the fact that he was also very funny. I certainly don't remember him using any foul language in the 60s and 70s when he was in the Humblebums.

I'm not sure there is actually that much bad language in the clubs these days. On the odd occasion when somebody has used the f word on a folk festival stage, there is a collective intake of breath in the audience. People are still not that comfortable with it. Maybe it's different in other genres.