... which is a totally reasonable, perfectly rational position. Further, it is a policy regime that has been achieved democratically.
Personally, I am very much in favor of infill. There is a lot of crappy two story housing stock in san francisco that has no charm and no aesthetic value and would lend itself perfectly to at least doubling of density.
But let's not talk about the opponents of this as if they are flat-earthers or white supremacists or something - their stance is just as reasonable as any other socio-economic-political view.