Find me one plant that has been genetically modified enough to make it as different from its original version as corn is from maize.
In addition, genetic modification only changes specific genes. Selective breeding ends up with a lot of other changes. As such, selective breeding is more dangerous for a given modification.
That's technically true, but in practice the results of selective breeding have undergone "staged deployment" - populations/farmers with harmful variants would have been selected against. Modern GMO can reach a global population much more quickly, so harmful variants have the potential to cause more widespread harm.
I was raised to believe that genetically-modified foods are unhealthy to eat and bad for the environment, and given a variety of reasons for this, some of which I now recognize as blatantly false (e.g., human genetic code is isomorphic to fundamental physical law), and a few of which still seem sort of plausible.
Because of this history, I need to anchor my credence heavily downward from my sense of plausibility.
The major reasons I see to believe that GMOs are safe are:
The major reason I see to believe that GMOs are dangerous is:
So: green goo, yes or no?