My problem with GMO crops has got buggerall to do with gene manipulation itself. The current GMO foodcrops are being genetically manipulated not for higher yields, but for greater resistance to frighteningly strong pesticides. Quite predictably this particular regime of blasting weeds with weedkiller that left "most" of the weeds dead have also now bred "superweeds" which need multiple times the originally recommended dose of GMO-crop pesticides to keep them at bay. The worst-case scenario is that this arms-race against nature is probably going to end up with some version of Paolo Bacigalupi's "windup" universe. At best we can look forward to an increasingly toxic food supply.
Reference : http://www.bbc.co.uk/news/magazine-19594335
There is something very fishy about this guy's sudden "enlightenment".