Yeah, but the thing about South Park is that Trey and Matt has this smugness about them that everything they say or represent is right, and if you feel the opposite of what they do, then you're an idiot that should go away. Seth's that way too, and, perhaps the last couple of episodes showcased his viewpoints more prominently than others have. I can't excuse it either.
And yeah, I do feel a lot of South Park episodes are preachy and often blissfully ignorant. Family Guy's just idiotic and moronic, and I go into each episode with that expectation. But at times, it seems like South Park can get away with a lot of things, and if Family Guy did the opposite (or even the same), they get blasted by commentators and couch critics as being the worst thing ever crafted.
Here's the thing about that.
The writer's reasoning for Meg's "born-again" attitude is because she was only exposed to the religious programs seen on networks such as TBN, Daystar, Worship, and others, which do tend to skewed towards right-leaning evangelical Christianity. The Way of the Master, Kirk Cameron's daily show, airs on a lot of those channels, and it, along with a LOT of those shows, does seem like it's perpetuating the so-called archaic stereotype of Christians wanting to convert everybody and feeling that everybody not like them are evil or unworthy to be in the same room with them.
This, coming from a Baptist from the South, grandson of a Trustee, great-grandson of a Deaconess, with cousins who are Bishops and Deacons, miles away from CBN HQ and Liberty University. Those people do exist. Some are in my family, and they do have these attitudes. But not all Christians are like that.
It's those Christians that are that dominate the mainstream, controlling the media and the message. The Robertsons, Dobsons, Hagees, Falwells, Camerons, and Bonzels of the world are the dominant Christian voices, and the ones who personify and embrace the stereotype.
Perhaps if Meg (and Seth for that matter) was exposed to more than conservative Christian programming in the "TBN/CBN" mold (although, to be honest, because the evangelical wing of Christianity has a lock on the Christian media market including the channels, progressive voices are far and few between), then maybe she would have been less of a stereotype, and maybe Seth could see there are more than one side when it comes to Christianity.