So may be we can start by making a differentiation here. GMO as an applied field of science may be a good thing. May be it can produce safe food but such does not automatically means that the industry is using the technology ethically. It seems to me that they are not so interested on feeding the world as they are interested in their own pockets.
Sorry to insist but a week ago, saying that car makers cheated on their emissions testing could have sounded like an environmentalist conspiracy theory. See the technology to make an environmentally friendly diesel engine is there, but there is a trade off. A trade off (low power) that if admitted openly, would cause the consumer to reconsider. The technology was applied during the emissions testing but not during normal production. What re assure us that the same isn't happening with GMO? This is where the problem relies. Allowing a corporation to toy with nature like this just because is safe could be a ticking time bomb. There should be more check and balances, at the very least, to ensure that a few greedy corporations are not going to dictate what we put in our mouths.
An example of that, I remember, was cited during the swine flu outbreak. Apparently the WHO has the power to remove patent rights on vaccines when a pandemic is declared, so that enough vaccine can be made available.