"I don't consider Hymns to be folk music" - West Gallery Music? Or Moody and Sankey for that matter?
I don't know which is the greater, the number of folk songs with tunes that started off in church, or the number of hymn tunes that started off as secular folk songs. Either way it's a big number, and some of the best songs in both traditions.
It isn't just us have these discussions - there's a controversy right now about "what is classical music?", with some records being banned from classical music charts, and disputes over what criteria should apply.
Actually, as terms go, "classical music" as a word which is supposed to cover all the types of music that it is used to cover is an extraordinary misnomer.
At least all the things we might variously describe as "folk music" are made by folk - whereas a great deal of music called "classical" just isn't classical in any recognisable use of the words, except as an arbitrary label. (That's not to impose a value judgement - but noone wopuld decribe the Millennium Dome as "classical arhitectire" - but the equivalent bit of music might well have the word aopplied to it.)
Then there is "what is music". Or "what is poetry?", just as endless a discussion.
The thing is, whatever we do, people seem to get involved with bringing things together that are very different, and using the same word for them, and pretending that because they same word is used they musrtt have a llt in common - and then other people, logically, try to breaking them apart again, because in fact they have so little in common.
The map is not the territory.