That's so old a joke it's impossible that it engendered a laugh from anyone who wasn't, like you, inclined to deliberately, and gratuitously outrage a large section of the public.
The Great Setanta is not so perfects as he sees himself that if delving was allowed and done, an issue/subject/relationship wouldn't be found that a smug and dismissive post tweaking the Great Set would result in him feeling outraged (and almost assuredly defensive) and insulted.
But Christians who believe Jesus to be their Savior and The Son of God, well they're all assholes and so deserve to be outraged and insulted. Especially if it tweaks one's sophomoric sense of humor.
Nevertheless, how courageous of an atheist to shove it up the noses of Christians in an obscure internet discussion forum.