I used to do it myself when i was "in". Or the born agains, they were hated even more i think. I think there's jealousy there because the Catholic church is so rich, more members and has a rich history. I dont believe in any religion but you cant just highlight negative aspects of another religion just to move focus away from ones own.
@pale.emperor, it's just like anything else that you know is kinda of wrong but it's part of the group enforcement and rationalization, so you do it.
I have friends who play the "At least we're not _____" card all the time, out of desperation, when they realize they have no other defense.
It is not a valid argument, it's just an annoying political diss. We should be better than that.