Many comments have pointed out that there are plenty of places on the web to have discussions about political topics, so let's keep the HN about tech.
I see the merit in this sentiment, but for me reading the political discussions within this community is something I value greatly. For one thing, there are a great many non-US based people here. In my experience I have been exposed to a relatively balanced set of perspectives, and generally commenters are thoughtful and un-troll-like.
In short, I learn many things from other folks in this community, and that includes political topics.