Just because it isn't against the rules, doesn't mean it's on-topic. Also, it's not the topic itself that makes me upset, it's the quality of discussion that usually follows. Most of the people lose their minds when they start to talk about politics. On HN this happens with social justice issues instead.
What, is it against the rules? No, I don't think it is. I think you should ask yourself why the topic makes you so upset/uncomfortable.