On rare occasions, I've had HN-quality discussions about both politics and religion. It's difficult -- you have to be relentlessly dedicated to civility, and quite selective about who you choose to engage with. I don't think it's realistic to expect it to happen easily, but it's something that can be cultivated in an invite-only setting.
I have managed to curate my Facebook friends to the point where I can have some surprisingly civil conversations there, even among people with extremely divergent views.
I like the idea of an online discussion group for political junkies like myself that is either invitation-only or aggressively monitored for civility. Maybe I'll have to make one.
If you create such a group, one specific guideline you may find useful, on top of standard stuff like "be civil", is "no labeling another person with any label they would not voluntarily apply to themselves". This helps to weed out subtle incivilities, like calling people anti-whatever, that people might otherwise feel like they can get away with.
