GMOs are neither inherently good nor bad, they're a classification term for an incredibly diverse array of things. It's like saying "person" or "human"--some are good some are bad, but the category covers a wide area, with many things under its umbrella. It seems that, much like the controversy behind vaccines/vaccinations (anti-vaxers), this is a concern for both right wing and left wing individuals. I think that a big part of it is more from the monopoly that a select few, powerful companies (monsanto et al) have on the GMO market and the word agriculture and food supply. Most foods made from GMO-derived seeds, of which Monsanto owns the intellectual property. I'd think that is the biggest and most understandable worry. Most people are chemophobic though and are ill-informed believing that any manipulation is "unnatural", which does not necessarily mean safer. GMO as a technology is completely ambivalent--it has the potential for just as much good as it does harm, but the question is if groups like Monsanto are responsible, benevolent companies that will use their power for good, or are they just concerned with profit and willing to sacrifice people's health/safety to make quick profit. Definitely, like everything, these things should be closely examined and investigated to see how they affect human beings. People should be very concerned with what goes into their body, but often these same people who are against GMOs should instead be concerned with all the much more pressing problems of their regular diets--red meat, processed food, trans and saturated fat, hydrogenated oils, fried, fast food, over consumption of alcohol, dairy, and fructose. Hell, even many "health foods" can be bad for you in abundance, like kale.