You have this backwards. If companies are going to introduce new products into our food supply, the burden of proof should be on them to prove that there aren't any negative health consequences.
Is it harder to show proof of absence? You bet your ass. And given the ramifications involved, it should be.
Look, I'm not an anti-gmo crusader. I think it has a lot of promise to more efficiently feed a growing world. But, like any technology, it can be used both responsibly and irresponsibly, and the private sector doesn't have a great track record of putting public health ahead of profits.