If you want to do whatever you want with your field, don't enter into contractual agreements where you agree to follow certain rules.
The farmer had not entered into any contract with anyone, that is the point. It's not his fault if pollen from his neighbor's field entered his field, even if they contained "patented" technology.
"Well but you decided to be born, and live in society!" Is not the definition of "you entered a voluntary contract" that most people would use.
Just admit that your initial response about contracts, was wrong.
Instead, you shouldn't have said anything about voluntary contracts, and just said that you support whatever the law says and the governments monopoly on violence, no matter what, because "democracy" or something.
So this part here:
"If you want to do whatever you want with your field, don't enter into contractual agreements where you agree to follow certain rules."
This part is not possible. No someone cannot do this. So you suggesting that they go do this, is wrong. Just admit that.
You don’t need a license to use patented technology which you either bought from a third party, was given or has blown onto your land by the wind.
You can shrug and say "Oh, it was clearly an accident, Monsanto is evil". And Monsanto is certainly evil. It's just reasonably clear why the judge would view this behavior as deliberate and knowing infringement of a patent.
"I should be able to do whatever the fuck I want on my field as long as I don't use pesticides or processing that has been banned by law"
And then someone responded to this by saying that someone signed a contract.
And then you responded by going off about something that is refuted by the original statement.
So, you need to agree that the original response about a contract was wrong, and also that your new statement is irrelevant.
For example, you should not deliberately cultivate a patented plant for which you lack a license from your neighbor's plot of land and then treat it in a way that only makes sense if you're doing that. That will incur liability when a judge notices you are trying to dodge licensing. To put it another way, using processing banned under law.