Sinister Supporter: a remarkably longwinded version of the argument that used to exist in a rather shorter form; "all music is folk music, I've never heard a horse sing a song".
However, most of us can spot a qualitative difference, both in in form and historical function, between the Wild Rover and Eleanor Rigby. And a lot of us choose to call the former a folk song, but not the latter. If you can't detect that difference, there isn't much point in discussing it.