If they were dangerous to sing then they were dangerous to write. Ipso facto, I don't think many of them existed in the first place.

One or two exceptions do come to mind however, in the form of Luddite songs and Captain Swing songs. I suspect thoughh these would have been sung in highly clandestine circumstances. Also, in Ireland especially, quite a few songwriters got round the problem by not naming the object of their sedition and dressing them up as love songs or as laments for their dear departed blackbird or whatever.