"Rent seeking" doesn't mean what you seem to think it does. Rent seeking means to try and extract rents from a process that would have happened without you. Rent seeking would be if the farmer had, through traditional agricultural processes, come up with a seed that had glyophosphate resistance, and Monsanto had sued him on the theory that they owned the patent to glyophosphate resistant seeds.
But that's not what happened. Without Monsanto, the glyophosphate resistant seeds in question would not exist. The farmer in question was free to use regular old soybean seeds and get regular old soybeans. Nobody forced him to use Monsanto's seeds--he did so because he got a benefit from them, a benefit that was the result of Monsanto's invention and its investment in R&D.
It's not so black-and-white as this. You can typically buy excess seeds from the local grain elevator for replanting; these now contain an unseperable proportion of the descendants of Monsanto's seeds, so it's at least become lot harder not to use any of them.
In other cases (not this one), the farmer's field has been cross-contaminated from nearby fields of GMO soy, so they have been forced to use the descendants of Monsanto seed. Are these cases different? Why, in patent law? (Patent infringement does not require intent).
The environment that Monsanto are trying to create is one in which you must pay a royalty to Monsanto if your crop contains any of the descendants of their seeds, and where completely avoiding their seeds is impossible or at least very difficult (and imposes new costs).
But that's not what happened. Without Monsanto, the glyophosphate resistant seeds in question would not exist. The farmer in question was free to use regular old soybean seeds and get regular old soybeans. Nobody forced him to use Monsanto's seeds--he did so because he got a benefit from them, a benefit that was the result of Monsanto's invention and its investment in R&D.