It's not about nutrition. It's the risk that hidden risks that GMOs engender. E.g. Unknown effects upon the ecosystem.
Another example: GMO Wheat contains an unnaturally high gluten content. Gluten is an irritant for everyone--some more than others. We have many people who are not really "gluten intolerant", but think they are. They are just sensitive to the unnaturally high gluten content in GMO foods.