Uuuuh. They are saving the world. If it is a choice of dying of starvation at 12 or getting weird diseases from GMO food later in life, I'd choose getting weird diseases later in life, thank you very much.
Folks in the US, Western Europe, Oceana and a few other places are lucky enough that we are so rich we can care about what we eat, and we can afford to be picky. Most of the world isn't that lucky. Is eating GMO grain healthy? Absolutely, compared to dying of starvation.
Primal and Paleo is eating about what is best when you have the options. Heck, I'd even love to see mandated labeling in supermarkets for GMO food, etc. But to say the practice is evil is a bit myopic.