Yeah, proven by expensive studies that were funded by the company making the GMO. Who is going to pay for another study to try to disprove it?
There's a reason we sprayed DET all over our vegetables for years before it was banned: there was no scientific studies proving that it was harmful, even though it clearly was harmful in hindsight.
Science is not instant, and there's no way someone can claim that some brand-new GMO is "perfectly safe", without any long-term studies on its effects over 10, 20, 30 years of exposure. That's just not possible. And yet you try to explain it to these science zealots and they just brush you off as being "anti-science".