Ha. I actually thought to myself after writing that, I bet seekingferret brings up the Song of Songs... but I think it's a quite different thing to use sexual love as a metaphor for God, than to use God as a metaphor for sexual love.

After listening to Judas (which I hadn't heard before, I suck at popular music), I don't think I would mind it being reworked as much, and when I sat down and tried to figure out why, I think it comes down to personal reasons: because I really love "Hallelujah," I have a kneejerk reaction against trying to appropriate it. (I suppose I'd feel the same, only much more angry, if someone tried to repurpose the Bach B Minor Mass for a romantic secular song, or something.)