Organic farming can also use pesticides (and most do), some of these pesticides are as bad or even worse than the ones used in modern agriculture.
And in regards to nutrients https://gmoanswers.com/studies/how-do-gm-crops-impact-soil-h...
From the SA article:
“Efforts to breed new varieties of crops that provide greater yield, pest resistance and climate adaptability have allowed crops to grow bigger and more rapidly,” reported Davis, “but their ability to manufacture or uptake nutrients has not kept pace with their rapid growth.” There have likely been declines in other nutrients, too, he said, such as magnesium, zinc and vitamins B-6 and E, but they were not studied in 1950 and more research is needed to find out how much less we are getting of these key vitamins and minerals.
That doesn't mean GMOs are bad but it might mean people will abuse the fact they will grow easily on just about anything (I'm exaggerating for emphasis).
As for the unfair advantage it is in large part because of ignorance of the consumers. I admit it is a weak argument but sadly the local farmers often have to grow non-gmo because that is what sells and they will get lower crop yield if there are other nearby GMOs (bugs and cross pollination). It is not enough to be locally grown... you have to be GMO free. I met a farmer in Hawaii Kauai that shared this issue with me and the seemed fairly passionate about it.