1. You seem to think that consuming a GMO is a riskless way to save money. Consider reading "Assessment of the food safety issues related to genetically modified foods" by Kuiper et al. or similar to understand how scientists currently asses risks for GMO food, and then the history of any substance later discovered to be harmful to humans (I recommend Gately's Tobacco book). We have a lot of evidence but it is far too soon to call the GMO race, as the potential benefit is something like $3/meal and the potential cost includes things like cancer.
2. You are forgetting that PG also consumes GMO food, and that OP also runs a business.
3. In transactions engaged in by intelligent people, both sides believe they are getting more value than they are giving up. Because of this, your distinction between OP giving money to Monsanto and PG getting money from Monsanto doesn't matter -- both sides are benefiting more than the cost incurred.
4. Your second to last point ("If Monsanto's business practices bother you, factor that into your purchasing decisions") is obviously true, and exactly the kind of thing OP seems to agree with -- he has even taken it further and used those morals in the design of his own business.
5. "Monsanto is not the only beneficiary of their evil ways, though: because of their evilness, millions of Americans spend less on food than they otherwise would" ... and have an increased risk for all sorts of disease. See #1. What odds do you give that GMOs do not cause an increase in disease? In light of that number being non-zero, would you like to take back this statement?