If they become unwilling or unable to sell corn seed, buy it from another company.
What's the issue?
Monsanto's business model: You buy seed from company X or make your own seed. Monsanto sends private detectives out to take samples from your crop. If they find signs of patented DNA sequences which will happen because of cross polinization, Monsanto threatens to sue you into oblivion unless you switch to Monsanto. (Legally you're guilty of "DNA piracy" unless you can prove your innocance...It's your word against Monsanto's.) Once you switch to Monsanto, you sign a contract that prohibits you from reseeding your own corn. So you have to purchase new seed from Monsanto each year. Competing seed suppliers go bankrupt because all their customers were forced to switch to Monsanto. Repeat above over and over again in market after market until Monsanto runs out of markets to monopolize and farmers no longer are able to reseed. Profits!!!