It's a good joke on several levels.

It doesn't HAVE to be a religious joke, or a Jewish Catholic joke, but growing up in a majority Catholic area I always found a safe way to tell it cross culturally to the amusement of most.

It also carries a practical versus intellectual approach to issues, with the favoritism going to the practical 'cause that's the guy who gets the last word in the joke, even though he is just as wrong as the 'pope'.

And it's a slap to the learned men of the 'jews' who are all too afraid to go mano-a-mano against the 'pope' so that the job goes to either someone too simple or ignorant to be justifiably afraid. This is one of the reasons that the joke can be enjoyed by both sides, which makes it in my mind the equivalent of a parable.