As a one-off thing, this sounds good. Implemented longer, term, though, I think it would be trying to solve a problem by treating the symptoms. Politics isn't the problem, since politics is simply the process of making group decisions. The problem is not the
topic but the
behavior.
So what does good, relevant, political discussion on HN look like? What does bad (but relevant) political discussion look like? Then update the guidelines accordingly. Maybe the guidelines could even have examples.