If you're talking about "accidental contamination" like Percy Schmeiser, stop watching propaganda documentaries and try reading about the actual cases. There was nothing "accidental" about them.
No one makes or has ever sold sterile seeds. A gene is not "for" an organism. A gene is a sequence of DNA code that does something. There's nothing inherently "spider" about a gene. And here's the most hilarious part.
How do I know an increase in Vitamin A production is the only thing you added to your seed? I don't. And that is where this distrust comes from.
The simple economic argument is that it would probably be against a company's best interest to produce and release a foodstuff that was toxic or poisonous (which is why these things are tested for, sequenced out for verification, and chemically analyzed to check for this kind of thing). Not many companies make a good living on killing their customers. But even more basic than that, how do you know that your conventional or organic plant doesn't have a random mutation that makes the plant create cyanide? You don't. Why don't you distrust any of that? Because you don't know anything about biology or genetics beyond what you read at Natural News or Mercola. And these are the very sites that were screaming about this being genetically modified grass as their shining example when that was exactly not the case at all. Such credible. Wow.
Because she's so fat.
I have hardly ever known a mathematician who was capable of reasoning. -- Plato