The US is hyper-polarized. There are crazies on both sides. The bigger the city, the more political processes select for crazies. In a village of 100 people (1

The US is hyper-polarized. There are crazies on both sides. The bigger the city, the more political processes select for crazies. In a village of 100 people (1) more people are involved, since individual influence is felt (2) there are fewer crazies, since you can only go 2-3 std. div. out. In a bigger city, (1) fewer people follow politics, since there's no direct influence on their lives; civics is dominated by crazies. (2) The absolute number of crazies is higher. If you have 100,000 people, just by statistics, the craziest crazies will be crazier. Having a small number of very bad crazies can ruin civics, since they often operate outside of civic processes. If just one person is willing to tarnish your reputation, smash your windows, or send a death threat, that can have a chilling effect. The worst cities in the US are near-100% blue or near-100% red, since there's no moderating factor. Transient cities also tend to be worse (where a lot of the population don't expect to keep living there in five years), since no one cares about civics. SF is the sort of place people most people move out from when they decide to start a family. SF is close to a million people, VERY blue, and that leads to extremist politics. Note: I'm extrapolating from what I see with cities where I live, as well as accounts from SF. I don't have first-hand experience there. But I think there are a lot of reasons why SF politics might get particularly broken.