You're a little late to the party, pal; and you are wrong.
Actually, I'm not sure he is wrong.
I've made the same mistake, Howlin, in 'defending' and trying to explain South Park to people who don't 'get it'. It's easy to say "Well they make a point of insulting everyone and everything" I've done it too, even recently. But it occurs to me, that to make that our line of argument is to miss the point ourselves.
Their targets for insult are not random, and not casually thrown around until everyone gets hit just for the sake of hitting everyone. That would imply they have no real creativity, and no real point. I think they do have a point. You may agree or disagree with the point, but I wouldn't argue that they attack equally. In fact, they attack without mercy and without apology those who they think ~deserve~ it. And that's an important distinction.
The actual target for the insult might not be who you might think from seeing only a singular quote or a singular scene. The Mary statue scene is a targeted parody to mock people who think they should flock to these apparitions and pray to them to cure what ails them. That's the target. And that target is effectively and vividly insulted. Not Catholicism, not Christianity, but a particular group within those faiths have been called kooky and their apparitions have been called fake. If you are one of those people, you've been targeted. If you are merely Catholic, you have not been targeted here, but I can understand if the imagery is too much for you.
Along those same lines, Cartman insulting Kyle or becoming a Nazi isn't really an affront to Jews... Kyle is a more sympathetic character than Cartman is. It's a parody of anti-semites. It's Cartman that is the villain, not Kyle.
Some Jewish stereotypes are laughed at, Kyles mother and cousin, for example... but they aren't "Judaism". They are caricatures of an American type.
People who are those stereotypes might be offended. But the stereotypes exist. And, over the long term, I think the portrayals are sympathetic. Kyles mother and Kyles cousin, and Kyle himself, are not evil characters. Cartman is :~D
So I'm arguing from a different point of view now. Let's first make sure we recognize who is really targeted, and only then can we really argue the merits of the point that was made.
Kyle's mom is a nattering parody of every neurotic Jewish mother sterotype I've ever seen.
"I've made the same mistake, Howlin, in 'defending' and trying to explain South Park to people who don't 'get it'."
Yeah, but the problem with that statement is that I DO 'get it' and am a huge fan of the show!
The rest of your post, though, is spot-on.