My take is, flag these topics off the site. Cut them off like a gangrenous limb. We want to keep the leg, but even more, we want our heart to keep beating.
But then, a vocal subset of HN users is offended by the idea that story upvotes don't mean it's OK to debate libertarianism vs. liberalism here, so don't misread this comment as prescriptive. We're not going to fix this problem. I'm also fine with that.
Ed's right too, of course. Are you here to hear what the average HN'er thinks about Steve Jobs? No, you're not. I read HN in two ways, both of which still work for me:
* I scan for stories I have something to contribute to, and
* I read a shortlist of users whose presence on a thread have been reliable signifiers of quality. (The list is on my profile.)
Try doing that. You'll miss a lot of HN; a good thing!