Quick, imagine what Bad Religion sounds like! Next, imagine what they would sound like playing various Christmas standards! If you have heard both of these categories of music before, then you have heard this in your mind already. You could probably perfectly recreate it mentally with no problem, irony intact.
It's pretty funny to hear Greg sing these religious tracks. It's basically the same concept as Me First and the Gimmie Gimmie's (or 99% of punk cover songs) -- the original melody sped up to punk rock standards. Decent. Will be good for a play or two in December.