But he signed a contract saying he would only buy the modified seeds from Monsanto and their resellers. He explicitly agreed not to do what he did.

If it were a third party farmer who hadn't signed a contract with Monsanto then this case would be completely outrageous. But that's not what happened.

I don't think the case is about the seeds as much as everybody has made it out to be. He previously signed a contract limiting the ways he could acquire modified seeds, and he broke the contract.