In politics generally, there's much more incentive for a small interest group to lobby[1] or advocate for a policy that provides a concentrated benefit to the group, than there is for the whole population to fight back to eliminate the small per-capita cost of the policy to the population. Also, many of the voters in SF have at least progressive sympathies, which include not "oppressing" groups that are seen to be "oppressed", even if they happen to break the law or make life unpleasant. So lots of money is spent in an ineffective but superficially compassionate way.
[1] In the broadest sense, not at all restricted to professional political lobbyists.
Sounds like the sympathies of the majority of the voters play a significant role, and not only the "advocates", as the other commenter suggested. Or at least as I understood it.
[1] In the broadest sense, not at all restricted to professional political lobbyists.