From everything I have read about Monsanto (none of it from Taleb), they are a pretty shitty, unethical company. They have ruined the lives of farmer in many places inside and out outside the US. I mean, round up is illegal in the EU.
His issue with GMOs, as I understand it, is mother nature "developed" and evolved these crops over a long period of time, and we should not trust a few IYI scientists at Monsanto, etc to play with that evolution via genetic manipulation.