Having lived on the fringe of the fringe of society (I was "the guy with a job" in my circle) for about a decade, I can tell you from observing others that there very well may be no limit to the capacity of the human mind to dive into self-delusion, regardless of any amount of contradicting "evidence". In other words, when presented with a simultaneously "incontrovertable" and "suicide-inducing" whatsis, the majority of people would pack it away. They would blank it out. They would "see" it as something different. They would "get over it". They would say that somehow, something other than a complete picture was given. This is how we survive as a species.
Unfortunately, the majority of people are of the delusion that "normal" human beings have a good grip on reality. This has actually been disproven, to some extent. Real-world, peer-reviewed, repeatable and repeated studies have shown that "normal" individuals routinely and repeatably overestimate their abilities and capacity. That is, they have an unrealistic and inflated view of themselves. Those with "low self-esteem" (the ones who are "abnormal") score much more accurately in tests of estimated ability vs. measured ability. The amazing thing is that, the greater the incompetence in a field, the greater the overestimation of personal ability in that field!
Therefore, I'd say that the majority of human beings, as they are "sane", would invoke these delusional measures to defend themselves, and would do so successfully. It would only be the abnormal who would make the mistake of accepting these "facts" and thus ensure their own destruction.
We need delusion to get through the day. We need an incomplete picture to make any decision. An enormous amount of our sensory brain regions is NOT involved in "sensing" the input. It's involved in EXCLUDING information. If all people noticed everything at all times, if they were truly perceptive, they would have a very hard time living in our society. Imagine what it would be like if you were aware of the feeling of your clothes on your skin at all times. Imagine what it would be like if you could not look at a word without reading it--you just couldn't shut down that part of your brain. Imagine what it would be like if you heard and noticed every tiny sound around you. (Some of us don't have to imagine it, but it can take decades to develop intentional filter mechanisms, if they ever appear at all.) We are, as a species, well-adapted to IGNORING information and not bothering to incorporate "knowledge" into our world views if there is no apparent pressing need to do so.
That is why I opine that there is probably no such thing as "knowledge so terrible that merely knowing it will destroy all humanity".