You have the freedom to choose someplace affordable before you move there. Telling someone who's already been living in SF, with roots dug in, maybe owns some property or has a long-term job there to just up and move is incredibly selfish. Moving is incredibly expensive.

The problem is not the new people moving in and the solution is not to stop them, the solution is to address the pressure those new residents create that is driving the old residents out. Entire families shouldn't be uprooted and have their lives thrown into disorder just because some twenty-something wants to live in SF for a year or two while they're working at a startup, and that twenty-something shouldn't have to practically evict some low-income family to find an apartment.