I don't think it's a song strikers would actually write, given that strikers and blacklegs will always have to work together eventually (not to mention living in the same community).

In this village, in 1926, a bunch of striking miners got together to make a bloody great gravestone with "BLACKLEG" on it and stood it up in a blackleg's front doorway. Is that so different from what "The Blackleg Miner" says? And is it so unusual for a village to contain groups of people who hate each other's guts?

(I've no idea how far back the song actually goes - but you can't decide on the basis of expressed attitudes in that way).