Dick Greenhaus almost always says what I wanted to say, and says it better. Or Art Thieme seems to, although he also waxes poetic enough so I can't always understand him.
But try this. There are good singer-songwriter bits. There is truly fine pop music. "Bottle of Wine" is a truly fine singer-songwriter thing. It isn't "folk music," though. The music in "Cold Mountain" was very fine music. And I'm extremely grateful to the people who made "Cold Mountain" for calling it Rock and Roll, not "folk music." Fine rock and roll music it is. It is not what people listened to at the time of the Civil War, and doesn't pretend to be.
If I am a "purist," it is not because of some theoretical belief about "folk music" or "traditional music." It is because listening to a song, or a singer, pretending to be what it is not is like listening to somebody scrape their fingernail across a blackboard. When some high school music teacher writes and sings a song about how he/she is an experienced and battered old miner/shellback/convict and knows all about life and suffering, it is phoney and offensive because the writer does not share the life experience or musical tradition of the subject, and immediately falls into bathos and sentimentality. Bob Dylan is a particularly vivid example, because he is a talented poet and an excellent singer. But he spoils all that by being a Capital-P Phoney and pretending to be what he never was.
I listen to, and sing, traditional music to try and get into the head of the person who wrote and sang the song, and feel what that person must have felt. I sing for the love of singing, and I don't try to impress people.