That's interesting. It's almost exactly what Bert Lloyd said. Folk Music differs from other music as day does to night, but when does night become day?
Having your own musical parameters is not only necessary but practical, as you have said Jim.
When all is said and done it boils down to this for me. We may not know what Folk Music is, but we certainly know what it isn't.
That said I try to judge everything on it's own merits, and not be too upset if it crosses my red lines, unless it's racist.
Oh Lord! What do I say about Johnny Doughty singing 'Will you marry me?'
'If I were to buy you a big Black N****r
To wait upon you and cook your dinner,
Then will you marry &co

I've just censored a Folk Song! Jim you are correct there are no easy answers. The more I learn the less I know.