Trouble with using a dictionary is that it only gives a snapshot in time. Definitions change over the years. When Chaucer used the word "nice", he mean't "not very nice at all" but since the 17th Century the word has had positive connotations. In our own time words like "wicked" and "bad" have been used in a positive way. It's all very well saying that people using such terms positively are wrong but common usage will override any Cnut trying to hold back the tide.

It might well be that the terms "Folk music" and "folk song" have more than one meaning now, and all we can do is treasure our own without being arrogant enough to tell the other fellow he is wrong.