That doesn't mean politicized topics can't be discussed—obviously they are and should be, up to a point. But such discussions tend to consume everything else with their flames, so we have to be careful about not letting them take over HN completely.
The best way we've found so far to draw the line is the 'primarily' test. When an account uses HN primarily for intellectual curiosity, i.e. for encountering and discussing interesting things, it's not an abuse of the site to occasionally talk politics too. But if it's on HN primarily for political battle, then—regardless of the politics—we ask the user not to and ban the account if it doesn't change.
This turns out to work well because there's a gap between these two kinds of user. The first kind tends to remain curious and substantive even as topics get more divisive. The second kind tends not only to drop the gloves, but to come armed with talking points and not be interested in conversation for its own sake. The one group fits the purpose of HN while the other does not. There are exceptions, of course. But the rule holds up well enough to be a fair standard for moderation.
More on this at >>16185062 , https://news.ycombinator.com/newsguidelines.html, and https://hn.algolia.com/?sort=byDate&dateRange=all&type=comme.... If you'd read those (especially the guidelines) and take the spirit of this site to heart when participating here, we'd appreciate it.