I mean some important truth underlying the rant. I'm not implying that there was one here. The point is that even when there is, it makes the destructive effects of ranting worse. It discredits that truth for those who don't see it and excites mob responses from those who do.
Patent trolls are lousy, but going on HN and posting a long-winded rant about how they're literally software hitler and should be tortured and then executed does nobody a service. The core of my complaint (patent trolls hurt small innovators) is debatably valid, but the way I'm expressing it alienates those who disagree with me and makes those who would otherwise be my allies shut up in fear of being associated with my jerkishness.