I doubt that a farm will make SF rent any more affordable, while new housing will. Building temporary structures is a great use of an underutilized backyard, but there is no way that a plywood hexayurt will last 200+ years like an actual building will (not that your hexayurts aren't awesome, Morten).
There seems to be a group of people who are intensely interested in agriculture, but only if it will lead to a confrontation with the police. There are also people who have strong opinions about the zoning of neighborhoods they do not live in, despite never having attended a single planning board meeting.
OSF, to me, was less hypocritical because the stated aim was always occupation as a means to protest greater societal ills. Squatting in empty buildings also makes some sense because the space is not being utilized. Blocking construction that will make the city more affordable, while sustaining well-paying unionized construction jobs is handwavy posturing.
-Jehan