"Folk music is also by its very nature changing".You said it, Cap'n. Clearly that change is part of your personal definition of folk, as it is of mine. Other people, however, think defined pieces of music like the new product of a singer-songwriter can also be "folk". I, on the other hand, say "wait and see". Herein lies the difference that sets off the arguments.
    Dictionary definitions change, you point out.Of course. A dictionary definition attempts(in England at least) to explain how a certain word is used by present day writers and speakers. So naturally, as usage changes, it will need changing. But here, we are talking about the definition of a word, which in this case happens to be "folk". That is a completely different philosophical thing from defining a genre of music. One is a word, the other is a kind of music. Just as, in the analogy I used earlier, "zebra" is a word, and it is also an animal. So the definition of the word is a different thing from the definition of an animal, because words are different things from animals.
   To put the matter simply, "folk" is a category, and it is also a kind of music.You have to be clear in your head which you are talking about at any one time. One is a label on a record bin, one is a noise you hear with your ears.