How is 15 years of no apparent health effects unsubstantiated? The way I see it, the burden is on the opposing side to prove that there IS problems with GM foods. What you have learned and "logic" isn't enough for an argument, it's gut reaction. It seems as though most of the opposition towards nuclear power is due to an association with nuclear weapons (unrelated) and Chernobyl (a poorly run plant in a backwards Soviet nation). Argument against genetically modified food is similarly based on some unrelated Frankenstein nightmare and slippery slope arguments.
Right now there's a need for GM foods, there might be negative consequences (guess what; evolution occurs everyday in nature as well due to varying phenotypes), the risk is worth it and being held back by paranoid fanatics and sensationalist media is disappointing. Like I said before, there's a risk involved in everything. The microwave could alter the expression of genes in my children, but by god, I'm not going to stop using it.
In the end, if I was going to side with the FDA or paranoid fanatics, NASA or hippies worried about nuclear plants on the moon, the Warren Commission or conspiracy theorists, I know where I'd put my money (psst...it's the educated people who know what they're talking about, not the laymen who dispense opinions in between Friends episodes).
At the time, GMs were, relatively speaking, untested or tested poorly therefore they should not have been implemented at that time and this corresponds to negligence by the FDA. Changing gene sequence may change multiple phenotypes. As you change DNA, protein synthesis is greatly affected. Isomers, for example, can mean the difference of digestion. You also can have different protein structures. Change gene sequences results in very chaotic changes to phenotypes. If these GMOs interact with wild types, you change allele frequencies. Science may seem as a slippery slope to one who doesn't understand it, which is why one is better off studying history.
Anyway, I support some uses of GMOs, I do not deny their ability for productivity; I've learned about methods for synthesizing insulin in batch reactors. My point is that by changing eukaryotes is very chaotic. You'll never know what exactly your product is and how they influence consumers, as eukaryotes can vary greatly depending on their substrates. Using biotechnology for synthesizing vitamins, minerals, etc. is much safer, as you can isolate your product much more easily. Bacteria are much simpler to work with because changes are readily observable. Toxic substances, such as heavy metals, organic compounds like BTEX, etc. can easily be identified and have measurable effects, unlike GM foods, due their nature.
But anyway, since you agree with what Conservationist has said, we need not argue further, as that was what I attempted to argue with you, but you obviously got lost in translation. I also agree that media sensationalism should not be trusted, so I really have no idea what you were trying to argue other than taking it in the ass by multinational monopolies.