Wow, you've got it COMPLETELY backwards. Peter's meanness is not only tolerated, it celebrated on Family Guy. He's a completely unsympathetic character. He doesn't love his kids. And the only times he ever gets what's coming to him is (sometimes) when he's mean to one of the "cool" characters. When he's mean to one of the "uncool" characters (Meg, Chris, Mort, basically anyone who's not good looking except Peter), more often than not the other cool characters (Lois, Brian, Quagmire, etc) laugh it up with him, and the audience is just left feeling bad for the victim. Half the time it's feels like the writers think they're the cool kids in high school and they have to make fun of all the uncool kids.
Roger is FAR more sympathetic than Peter. Even if he's completely selfish and calculating, they make it a point to show him as a sympathetic character and they don't make him out to be one of the "cool kids". You see the negative effects of his behavior (his lifestyle, alcoholism, addictions, self-hating rants, etc), and that makes it far easier to laugh at him when he doesn't learn. Furthermore, he doesn't have the other characters of the show edging him on and laughing it up with him when he does something mean or selfish. Unlike Peter, you're not supposed to laugh with him against his victims, you're supposed to laugh at him for being so calculating over what's usually very petty issues.
And there's no way you'll convince me that Roger is the reason AD isn't popular. By that same logic, Bender was the reason Futurama wasn't popular when it was first run on Fox. They're basically the same character (mean, calculating, never learn, but ultimately sympathetic). In fact, the reason AD isn't popular is probably the same reason Futurama wasn't initially popular - casual viewers see it as a lesser spin-off of their more well-known predecessors (even though they're not truly spin-offs). They look the same on the surface so people don't feel compelled to watch it (this also isn't helped by the fact that neither had a favorable timeslot - Futurama at 7:30 usually and AD after Family Guy at the end of Fox's primetime, people could watch the Simpsons and Family Guy and avoid both of them easily). My hope is that, now that American Dad is seeing a lot more syndication recently, more casual fans will start to realize how good it actually is (like what happened with Futurama, only after it was cancelled).
I guess I should say something about the episode so it's not a total thread disruption. I thought the Stan/Roger story was great, Stan's revised memory of his Christian camp was especially funny. Steve's B-plot felt very forced, but still pretty funny. And once again Haley is nowhere in sight (boo).
