If McGrath thinks slip(9/8)jigs are not ethnically English, he needs to get out more. The English tradition is/was full of these tunes, as is/was theIrish. The rhythm does slowly seem to be going out of fshion compaered to ordinary jigs and reels, but that's another story.
    Azizi says in this thread that white people are welcome to sing black folk music, but I dont seem to recall her taking that line in the "Pick a Bale of Cotton" and "Black Betty" Leadbelly controversy. But maybe I misremember.