We have two matters: 1) the actual claim made, which is very carefully couched and limited, and even then debatable
2) The use of that claim in even supposed "scientific" public discussion, by educated and normally alert people, for promotion of GMO deployment.
Regarding 1}
Consider: when talking about all this evidence and experience, they are talking about exactly two genetic modifications - glyphosate resistance and Bt expression in crops. They are declaring a lack of evidence as evidence - which is a perfectly good argument if (and only if) evidence has been carefully and adequately sought. To argue that such evidence has been sought, as is central to the claim, we are offered this website of thousands of studies - overwhelmed by quantity.
So: Without considering the provenance and dubious nature of many of the studies, ignoring that large factor, and just looking at a couple of indications:
There has been as yet no long term consumption study of the overall effects in a mammal of a diet dominated by either one of those modifications, let alone both in combination.
There have been no reliable epidemiological studies of consumption in humans, capable of detecting unpredicted effects of the kinds we have discovered in other large scale dietary changes (example: trans fats). That is partly because there has been no reliable labeling, which is necessary for determining distribution and exposure - it's been difficult to establish things like control groups.
The effort required to adequately study environmental effects would be enormous, and has barely been scratched - notice that when the bee death epidemic hit the headlines, careful studies on the effects of both of those two GMs (even the insecticide one) had to be started. They had been deployed, two thirds of the US farm landscape covered by them, without adequately studying their effects on honeybees, the best studied insect on the planet.
So their method of argument - offering a large pile, that we are expected to sort through, and telling us there's a pony in it - seems a bit dubious.
Regarding 2}
The basic argument of the PR operations is bad. Radically and obviously bad. Dangerously and overtly irrational, poor reasoning in support of a confused agenda under manipulation by powerful interests with much to gain.
Even if the two - count them, two - basic genetic modifications (glyphosate resistance in domesticated crops, BT expression later on likewise)
for which the basic environmental and human medical testing has been anywhere near informative (let alone sufficient), and the time line long enough to have had anything close to adequate real world experience, and the marketing or deployment practices familiar enough to observe and analyze,
were known to be "safe" thereby -
which is silly, btw, nowhere near -
that would not even begin to justify the conclusion that "GMOs" - all of them, in all the biological variety of the biological world - were "safe" - no matter how marketed or deployed.
The assertion that "GMOs are safe" is utter nonsense - an impossibility, an obviously insupportable claim on straight reasoning let alone in the real world circumstances in which it is made.
And it is being made, with these scientific websites and so forth as support -
in my area, for example, when glyphosate resistance arose in major weeds (an obviously likely and predicted consequence of the actual mode of deployment of the GMOs involved, which was denied (until it happened) by the corporation profiting from the deployment) another GM was developed (actually, had been under development in advance, for some reason) involving resistance to the herbicide 2-4D. And this one was simply rolled out with a couple of quick checks, under the cover of the supposed safety of "GMOs" as demonstrated by the studies and experience with glyphosate resistance - only quick and sharp public criticism caused the Feds to review and renege on their approval, which at last report was still pending.
This entire issue is one of those strange matters - we saw it most clearly with nuclear power, but there are others - in which the technological promise of a new field blinds technological experts to aspects of the real world that should be obvious to them.
