A tag? What, people can't read titles? If they see one post referring to any sort of world even they'll catch fire? Oh, horror, horror, politics thread.
Politics itself isn't the problem anyway. If someone wants to pick a fight in any subject, they can and will. We've had software threads that ended up much more a brawl than any politics thread.
However, I wouldn't object to a requirement for people to be able to provide some support for things they say, or at least be marginally informed before they express an opinion. Most really regular political posters scanning the headlines would do wonders as far as stopping the whole circular argument thing, since it generally only becomes "circular" when someone reaches the limits of their knowledge and resorts to a glorified form of "No it's not!". To which the only proper answer is "Yes, it is", followed by hypothesizing on their ancestry or sexual deviances.