If Monsanto can effectively quarantine their stuff,
That's been true down through the ages, it's how crossbred crops came to be in the first place.
It's darn near impossible to quarantine anything related to growing crops, whether its 2-4-D type herbicides which have been around since at least WWII, and can, under certain conditions, drift over a mile, down a ditch and do serious damage to someone elses soybean crop, or the more modern herbicides and insecticides which have similar problems.
Should the modern farmer be held captive by his neighbors desire not to use chemicals?
Yes, if they cannot use their product and keep their pollution on their land (pollution in the sense that it is a byproduct of the process they are using) then they should not use it.
When a painter paints a home with a portable sprayed, if the neighbor’s home is speckled with paint, it is not that homeowners’s issue, it is the painters problem to take responsiblity for.