The young “Gary” Keillor was raised in a very fundamentalist church, the Plymouth Brethren. But he left that, along with his original first name, long, long ago. OTOH, I think the guy is ready to bash in the head of the next Dane that does something stupid in front of him.
Of course, that should read, “that would be the 7th Commandment for Catholics and Lutherans.” (Thou shalt not steal.)
They only changed it on later airings on Fox itself. “Catholic” was restored both in syndication and on DVD.
The Simpsons children weren’t even baptised - I recall an episode where the Flanders plan to baptise them to redress Marge and Homer’s neglect. If the Simpsons were Catholic, the children would almost certainly have been baptised as infants.
What I didn’t understand about that episode was the apparently common belief (expressed independently by both Ned and Homer) that if Ned baptizes the Simpson kids, he’s legally adopted them. It has kind of a creepy Edgardo Mortara feel to it.
If that were true, it would mean that a heck of a lot of kids would be adopted by priests. While anyone can baptize, in practice it’s rarely done by layfolks.
[Homer]
***“Hey, Flanders! I got us some kick-ass seats down front!”
[/Homer]
How many times have I bitten my tongue instead of yelling that as I sit down in church?
I don’t think they’re Catholic, but I think they’re quite catholic. Maybe that’s what the priest was on about 
The Simpsons are Presbylutheran as established in at least one episode. Not that continuity is one of the show’s strong suits.