Great post. It's also worth mentioning Marxists like Ewan McColl who sought to rehabilitate folk music as what they thought of as true expression of British working class culture.
Reminds me of an incident many years ago. We were in the pub after a big Morris dance event. One of the Morris dancers was American, although living and working in England, and dancing with an English side.
Someone sang one of the regular "big chorus songs" and all the dancers joined in with gusto. Afterwards, the American started a conversation that went something like this:
American: "That's interesting. You know, the reason you sing that is because of the repeal of the Corn Laws in 1846."
English: "No, the reason we sing it is because it has a great chorus."
American: ""Yes, I agree it's a great chorus, but the real reason you sing it is because of the repeal of the Corn laws in 1846."
English: "No. It's just got a great chorus."
American, "But it comes from the repeal of the Corn Laws."
English, "Quite possibly, but I bet you're the only person in the room who knows anything about the Corn Laws. W singit because it has a great chorus."
This American chap had quite an academic approach to the subject. Elsewhere in the English folk world, there are many "unreconstructed lefties" still defiantly carrying the banner for causes from the 1960s and 70s — you may even see the occasional Justice for Blair Peach badge. Some of them make a point of singing songs that express their Marxist/Labour point of view. Thus, you get social workers and teachers singing rather too earnestly about working down the mines or int he cotton mills.
However, most of us just like to sing a good song, whether or not we agree with, or care about, the subject. Indeed, you get those same class warriors singing enthusiastically in the choruses of hunting songs, without apparent irony.
So, I agree with you, James H, that the concept of "claiming" or "hijacking" folk music for a socio-political cause is not solely the province of the wealthy and privileged.
Change of subject: thirty years ago, I worked in a corner office with a small group of people. I was born in 1962 and I worked with a woman who was probably 15 years younger. If I started to hum a Buddy Holly song (he died in 1959) she would join in and know all the words. I was (am) a rock 'n' roll fan, but she wasn't. She had just learned the words by osmosis, hearing them on the radio, or played by her parents. In a sense, Buddy Holly songs were her folk music.