Having skimmed through the article mediafactcheckbias linked, it’s kinda weird. At first glance it seems like it’s raising legitimate concern, but it never specifies what.
It sounds like it’s making a case that modified Bt toxins could cause unexpected problems in the ecosystem or for other crops on the long run by targeting more insect species than what it’s designed to, a seemingly valid concern, but never actually reaches any conclusion, instead it uses handwaves like "unexpected toxicological properties " and “protecting public health and the environment” which make it look like they want you to think GMO are poisonous to people without actually saying it.