It's hard to build new housing in cities like San Francisco. There's restrictive zoning that keeps developers from building too high. Plus, neighborhood councils get to object to specific projects they don't like.
These restrictions are a big part of why rents have gotten... too high. So a group of renters is pushing for a simple solution: Let developers build.
Only problem is, almost everybody hates it. In working class neighborhoods, people worry new development means gentrification. In richer areas, homeowners don't want high-rises blocking their million-dollar views.