The genetic modification is a technology. Whether the use of that technology is warranted, I think, depends on what is being combined. I would advocate using GM engineering to eliminate some invasive pests, like the spotted wing drosophila. A 5-year GMO effort would be worthwhile. But I would be skeptical of proposals to genetically modify plants to produce pharmaceuticals, like spermicide or insulin in rice.

I am OK with vitamin A being increased in rice, if there's testing that any changes in proteins or other constituents of the rice will not creating problems. For example, shellfish proteins cause many allergies. I would take a precautionary approach to those proteins being introduced into rice, without open, transparent, and peer-reviewed testing.

So the key for me is open, transparent, and responsive testing. New varieties of potatoes are tested to be sure they aren't producing too much solanine - and varieties have been taken off the market for that reason. GMOs should be treated no differently.