Your contention is belied by even the most cursory examination of political life in SF. "Perfectly normal, decent people" would never vote for that collection of deviates and moonbats who proudly fly the rainbow flag and put up street signs extolling the virtues of abortion.
Most people in SF don’t vote.
They are a majority of Asians who are either FOB’s (fresh off the boat) or are not citizens, as a very high proportion stay in permanent resident status. And even Asian citizens don’t vote much, being foreign born they believe in conforming to the local rulers.
And those people that do vote Democrat - a “normal” person certainly can vote in ways that their personal life wouldn’t predict. This city is full of people with unimpeachable personal lives that vote Democrat out of habit and out of conformity with the prevailing culture. Forgive them, for they really don’t know what they do.
And I live here, I know these people personally. My kids are friends with their kids.
It is plain fanaticism, by the way, to condemn people who don’t vote our way.