I remember when I first heard of the concept that you should not discuss sex, politics or religion in polite company. My thought then, which I still hold now, is that polite company sounds pretty damn boring.
It isn't a question of whether it is possible to have interesting conversations that do not involve those topics, I enjoy discussing a wide range of things. It is more that having forbidden topics as an indication of correct manners enforces a weird kind of false sterility on human affairs and I feel cheapens and narrows the culture that these manners claim to protect.
Someone who has seen lots of good forums wrecked by political bullshit. And to be perfectly clear, I do not mean "politics that I happen to disagree with", but politics, in general.
Fortunately, Hacker News is not a nation, and can censor all it likes to keep out all the crap.