I don't think anyone, not even Jim Carroll, is saying that someone should not be allowed to sing at all (although I can think of one or two...)

What I am saying is that there is a time and a place. There are the situations VirginiaTam writes about, where everyone is very friendly and supportive, and the fact that the singers aren't very good, or very talented, or very confident is overlooked. Believe me, I'm not knocking these clubs, they are an important part of what folk music is about. But there is another side, where people visit a folk club expecting to hear good music. If you want to get up and perform in that environment, then you should have a certain amount of ability.

They are different sides of the same coin, but they are different. The problem with some folk clubs is that too many people want to carry the attitude of the first sort of club into the environment of the second sort. It's this which results in floor singers thinking they have a God-given right to perform, and organisers thinking they have to get through all the floor spots before they can put on the guest who people have paid good money to see. It's this which results in the situation the OP complained of, where someone who's gone to listen to good music has to sit through a load of crap.