I take it you haven't listened to anyone pro-organic speak? Just a few short sentences with them and you would have been aware that they make outrageous claims regarding the health benefits of organic food. And it's precisely because of that that the onus is on them to prove it. And you can't just say "we don't have to prove it because we've always eaten organic and that's natural", err or whatever argument they use. That's a prime example fallacious logic.