there isn't really a mechanism. to me, that's the big problem - i don't see any theoretical reason to think that gmos would be more carcinogenic. there are some other low probability mechanisms (gene transfer), but nothing that makes sense on a 'causes tumours' level.

unfortunately, this is going to turn the gmo resistance (which has some valid arguments mixed in with it's invalid ones) into a conspiracy movement. it's been teetering on the brink for a while. big agriculture will be fingered as a villain, suppressing science for profit.

just like they suppressed tesla's free energy and cars that use water to split off the hydrogen on the fly.

the inevitable result is marginalization. and using logic is not a useful tool to combat it, as it just means you're standing with the conspirators.

http://www.nature.com/news/study-linking-gm-maize-to-rat-tumours-is-retracted-1.14268

not a convincing response.
http://gmoseralini.org/criticism-no-mechanism-for-the-effects-observed-has-been-established/