For the people who are having similar symptoms from corn as wheat/barley/rye gluten, there appears to be no coincidence. While the chemical make up of each grain differs, our bodies' responses do not. Thus, we insist that a connection must be made and/or there needs to be more categories to the condition. I think we've safely concluded on this forum that the range of symptoms for each person is wide, I don't think we really know why. That's why it's not totally an urban myth that corn is a problem for Celiacs.
I've tried having corn products that are free of cross contamination with wheat/barley/rye gluten and the same problem occurs. I even tried rinsing popcorn before popping--same nauseating result. I've had a bad relationship with corn since I was a kid, not sure how much GM corn was around then, but my hunch is that it doesn't matter. I couldn't eat corn on an empty stomach without a guarantee that I'd puke it up soon after. Everyone thought I had a weak stomach, go figure.
Also, something like teff grain, which has no risk of cross contamination like oatmeal and corn do, would ideally never cause problems. I've gotten sick from that. As someone suggested in my post on going grain free, the difference may lie in the amount of time a person has been unintentionally exposed to the problem foods.