What's the difference between a Rabbi and a Catholic priest? A Rabbi cuts them off, a priest sucks them off.
Why joke about Catholics?
Because the catholic priests have ruined my life and that of my countrymen. That's why I joke about them and you should too.
Even if you don't like Catholics it is hurtful to joke about something that many people take seriously and imply that they are sexually abusing children. You would be hurt if people made jokes about something that you seriously believe.