This is only when you look at it as a zero-sum game, which is only the case because there's not enough new construction happening. If you addressed the inequality between homeowners and non-homeowners by getting rid of the protections afforded by proposition 13, you'd create a situation where it's in everyone's best interests to have lower housing costs and we'd see more new construction as a result. As it is now, homeowners are actually incentivised to oppose new construction since it increases the value of their property.