Earlier quoted context omitted.
I'm not sure about that last part. In general the people who own single family homes in the Bay Area have had nimby opposition to more dense housing being constructed since more supply lowers prices.
More supply also increases traffic. This isn't just about everyone worrying about their housing prices (there are a lot of NIMBY reasons beyond that).
It also increases the need for new infrastructure, such as electric wires, sewer/plumbing, trash/sanitation, schools, police, fire stations, etc. You can't just plop Moar Housing down and call it a day. You need to build these things, too.