I'm not sure why we'd expect politics not to be highly contentious and divisive. It's life-or-death stuff. Do you force a teenager carry an unwanted pregnancy to term, or allow her doctor to kill an organism that is, at least genetically, human? Do we let unfettered immigration undermine the welfare state, or break apart families who are just trying to have a better life? What kind of legacy will we leave our children? It's bizarre to thing these sorts of questions wouldn't lead to fist fights.

I myself tend to get along with people with a wide range of political views. But I've always assumed it's because I'm a bit of a sociopath. I don't care enough to put other peoples' struggles above my personal relationships.