Political participants do not just have different norms of community participation: by definition, they have very different motivations as well. This is the real take-away of Politics is the mind-killer. Keep in mind that politics is a kind of conflict: it's about things that people actually fight over, in the real world. So the difference in norms may well be a consequence of these motivations: as the potential for real strife increases sharply, good deliberation becomes less relevant and "fairness" concerns are far more important:

This is why I very much agree with the spirit of this post: we definitely don't want to attract people who are just looking to win by diligently adding more recruits to their preferred side. At the same time, we can hardly afford to disregard the norms of political debate entirely; that's a recipe for being perceived as somehow "biased" and "unfair" by the general public when political issues do become relevant, despite our best efforts. IOW, the norms aren't really the problem. The best compromise, AIUI, is to cautiously encourage (1) the rise of factional blogs like More Right and Slate Star Codex as venues where folks can apply the skills of rationality to their favorite political perspective, while interacting "at arms length" with other sides, and (2) developing political mediation and conflict reduction skills at LessWrong itself, while keeping ground-level political disputes mostly off limits.