Sorry for the delay.
> cognitive toxin
I already regard much human intellectual production as «cognitive toxin» - and humans have the "modules" (I'll try to explain), even when underdeveloped. Now imagine that instead of a "human with them modules, whatever their state of development", you have a I/O box that inside has no actual intelligence (a critical "module"¹), no critical assessment of the quality of the output in all the required dimensions. (¹ "Intelligence" is actually more like a meta-module in this case, keeping more modules in check.)
It may compose a story that, mixing elements from its "learning material" that it blindly judges coherent, mixes typical and random. The real elements of the story, not those of the facts but those of the purposes, will be missing from the parallel structures. When a genius composes, all the structures are checked. When an unintelligent thing composes, those coded-in will be implemented and the others will be easily deliria, with disconnected crumbles instead of structures. A story is not just a succession of events, but a structure of meanings.
...The child, being Intelligent, will notice that and go "WTF?!". Or absorb monsters instead of intellectual products.
A text strong on the structure of "extended grammar of common language", but weak on the structures behind it, is «cognitive toxin», yes. The composer has to be Intelligent and see if there are faults - not just /formal/ faults. If an AGI had two parts judge and improve photorealism in a picture, it may work on making the building more credible, and be oblivious of the purposeless randomness of the situation of Julius Caesar helping Nixon roasting a skyscraper for a picnic of beavers depicted in (that this rarely appears in an automated composition because of the rarity of the links means nothing - a chain even of frequent events remains a random chain. And even a typical chain of frequent events would have no purpose per se).
A text which appears legitimate at a shallow regard may easily be a monstrosity when you consider it attentively.
Make an experiment: have a composer complex-ANN produce a story; read it and ask yourself (e.g.): "What does it teach you"? (This question does not exhaust the mess that could be behind a delirious composition, but is already an important indicator.)
> the English
Admittedly, I treat the language in a possibly uncommon way: I force it around the ideas I want to convey. I compose top down, not bottom up (not starting from the language but starting from the ideas and structures).