You are not so compelled. You have an entire supermarket, by your own admission, at which you can buy non-GMO foods.
But if your question is 'why can't I guarantee there is no biological creep between GMO and non GMO genes', the answer is 'fuck you, you don't get to demand that the world be shittier because you have an irrational bug up your ass' just like you can't demand to not have to touch anything a homosexual has touched, and just like you can't demand to be free from having to see women, or any other such irrational and unreasonable thing.
Thank you for your kind sentiments but you are vastly confused.
It is quite reasonable to assume that GMO genes are in fact being spread into other crops and into mom-target species. It is not a far reach at all to believe that there will be unintended consequences. And it is rational to be concerned that there is potential for those consequences to be delirious for at least some humans and for the environment.
Please let us not be confused about Monsantos motives, which are corporate profit.
Please let us not forget that big business has a long history of promoting the beneficial and sometimes 'beneficial' aspects of their products while sweeping valid concerns under the rug.
Look at Nestlé's promotion of formula for babies, first in the 'modern' west and then in developing nations.
If we are truly concerned about saving lives and promoting better health in developing countries, we would be working a lot harder at promoting access to reliable sources of clean water. We certainly would be doing more to prevent armed conflicts and political instability. I suspect Monsanto hasn't found a way to make a profit on those initiatives.