What I'm proposing here is an inclusive definition of Folk Music based on the empirical evidence.

I don't think you're proposing a definition at all, unless it's "Everything that's ever been heard (and enjoyed) by someone who went out that evening expecting to hear something called folk music".

I'm in two minds. I do like folk clubs - something happens there which is worth celebrating, even if you do sometimes end up listening to acoustic renditions of the works of Robbie Williams or heartfelt laments for the passing of apartheid. But I like traditional music more, and I think most folk clubs could benefit from putting on more of it.