McGrath:
"Bonniest Lass" from Merry Muses
"As I Came In By Fisherrow" from Herd
Pretty much any truly bawdy song.
"Tying a Knot in the Devil's Tail" (or Tyin Ten Knots...)
"Mad Tom of Bedlam" (or Bedlam Boys)
"Farmer's Curst Wife" (or Devil and the Farmer's Wife)

Likely you could find something fun about religion at the filk & Hash websites.
Almost any song that lauds non-God-inspired human goodness
@deadbaby songs
@hunt songs

But mostly a non-subtle, in your face, right out loud and non-cowardly "You know, this isn't a church. I'm Jewish (Muslim, Taoist, atheist, Sioux) and don't appreciate your prostlytizing here. Please sing a song or else take it outside into the street where that trash belongs."   I guarantee subtlety wouldn't work with people that determined to force their own notion of your needs on you.