As a simple example, many organic farmers use high doses of the organic pesticides Rotenone and pyrethrin to provide pest control. These have not been used for tens of thousands of years, and they are much less effective than industrial pesticides - which means that farmers need to use higher dosages to achieve the same result.
As a simple example of the fundamental dishonesty of the GMO promoters, that rivals the claim that all domestication breeding is "genetic engineering".
Modern "organic" growers overall use far smaller quantities, of far less toxic stuff, far less frequently, in ways with which we have far more practical and cultural experience, than industrial farmers using GMOs. GMOs increase the use of the chemicals involved, and the farming practices that rely on them.
http://www.enveurope.com/content/24/1/24 Suggesting otherwise, innuendo as a rhetorical technique, is not really something that should be excused or forgiven on a forum like this one. It's not a reasonable "error".
Along those lines, glyphosate was one of the "nicer" industrial ag chemicals, properly used - its being abused, overused, and eventually (soon) rendered useless by the current GMO ag is a shame as well as a hazard. Bt likewise - until recently one of the "organic" pesticides, a more benign pesticide used in spot applications, its effectiveness is being destroyed by GMO broadscale ag. It has no "organic" replacement, and its industrial replacements are nastier altogether.
The genetic engineers have been picking up the more benign chemicals, rather than the very most effective ones, to begin with - which shows they are conscious of the fact of risk here, and aware that they are not in control of this stuff. But that increases the loss, when we lose them.
It seems that toxicity of Roundup (and hence the instructions on the packet) is actually more relevant to the surfactant used to make glyphosate stick to the plant leaves:
This is true of the residue toxicity - the stuff one could in theory wash off. But with the glyphosate resistant GMOs there is also the incorporated toxicity - the stuff produced by the misinserted and broken and side effect code and auxiliary code within the plant, the stuff sequestered in the course of resistance metabolism, etc, inside the food.
Glyphosate works by blocking a particular enzyme that plants use to make aromatic amino acids. Animals don't have that enzyme, and have to get aromatic amino acids in their diet.
Some of the bacteria in the human gut seem to be capable of metabolizing various glyphosate compounds and derivatives and salts and so forth - with consequences as yet unexplored. In addition, glyphosate apparently chelates some minerals, suppress nitrogen fixing bacteria, and so forth, in the soil; and although it does not kill them glyphosate seems to reduce nutrient accumulation and disease resistance in the engineered plants - so that things like manganese and nitrogen become deficient, and things like Fusarium fungus excessive, in GMO crops. Also, yield takes a hit.
In high enough doses glyphosate poisons people directly, of course. But that is not the worry.