On Atrios' first point--presumably motivated by the talk of Amanda Marcotte's "offensive" blog posts about the Virgin Birth and so forth--I would offer one important qualifier to his general take: mocking the religious underpinnings of some political position is one thing; denying their sincerity is another.
Here's how the regression from mockery of politics to mockery of religion to mockery of religious sincerity tends to work: Some people hold abhorrent political positions that they justify with religious principles you happen to consider a bunch of atavistic Hooey. You attack the positions on their dubious merits. You then go over the brink and attack the underyling Hooey. But since you think it's Hooey, you go on to suggest that the Hooey, being Hooey, is just a mask for very different motives (e.g., misogyny) that can be deplored without discussion of religion. Not being a regular consumer of Amanda Marcotte's blogging at Pandagon, I can't say for sure this is her pattern, but it is common in criticisms of religious-based opposition to equal rights for women and/or gays and lesbians.
Whether or not this applies specifically to Amanda I'm not really sure either, but I do agree that questioning the sincerity of peoples' faith does anger them. On the other hand, appealing to the sincerity of their beliefs is a way of privileging them, to put them in the realm of privileged discourse, as well as removing the person's responsibility. I don't really care if the desire to discriminate against gay people, or turn the uterus into state property, is motivated by sincere religious conviction. I don't think religious conviction, sincere or otherwise, makes your beliefs somehow special. If you think your misogyny or homophobia is sanctioned by God, it doesn't make you not a misogynist or homophobe.
I've had this conversation with anti-choice progressives, who think it's important for me to understand that their anti-choice views come from a sincere religious belief. The thing is, I just don't care. The fact that your political beliefs are motivated by your religion doesn't make them special to me.
...adding, I didn't mean to imply that this "sincerity privilege" was something Kilgore was invoking. Here's an email from him:
Thanks for the discussion and the link. I do hope you understand I am in no way arguing for a "sincerity privilege." As you say, bad policies can and should be attacked on their own merits, regardless of their religious justifications. Sincerity is generally irrelevant. All I was trying to say is that arguments based on a denial of sincerity are best left to those who share the basic religious views whose sincerity is being denied. And as I noted, I'm happy to make those arguments every single day, not because I think they are critical to the political debate over abortion or gays rights, but because, as a Christian, I think they are critical to the internal debate over the meaning of Christianity, which happens to matter to me. I dislike our common enemies on more than one front.