Socialists and propertarians are using very different definitions of “land.” To us “land” means natural resources: one comes to own them when/if one is the first to mix one’s labor with them: i.e. homesteading. But to them, “land” means area in the abstract: i.e. not the dirt, rocks, trees, etc, but the actual area in an abstract geometrical sense. Their argument is that area is not a product of labor, and cannot be owned, and since area cannot be owned, it is a commons, and since use of anything in that area necessarily involves use of the area, whoever uses something in an area (which of course is anyone doing anything anywhere) is violating other persons rights to use the commons, and this creates a positive obligation, such as a tax that has to be paid to “the community.” Note that, to be consistent, they have to make the same argument with respect to volume that they made with respect to area, so you end up with everyone paying a tax for everything they do, including a tax for literally taking up space. Aside from the absurd consequences (or not so absurd if your goal is totalitarian socialism?), there are massive problems with the argument itself at every level, but that horse has been beaten to death, butchered, and shipped off to the glue factory. See the following threads: