"A person who would make that failure of reason cannot avoid making that failure of reason, since their thoughts are not efficacious. Thus, anyone who would be fatalistic upon learning about determinism could not be anything other than fatalistic upon that assumption of knowledge if determinism is true."
I completely agree. This doesn't detract at all from what I said, one of the causes that would be arguably inherent in this situation is whether or not the person has the capacity of reason to see a difference between determinism and fatalism.
"How do you handle the challenge of qualia?"
They are unobservable and unquantifiable, and there is no meaningful definition for qualia that assures people are talking about the same thing. Which definition of qualia are you referring to?
"The question is only, *in this case*, is it right to insist on the truth, or are there greater imperatives in play?
You are asserting that we shouldn't reveal the truth based on your idea that people would act more negatively, and equally that a deterministic scheme fails to provide a meaningful alternative. Perhaps it would benefit me if you illustrated your evidence for making the claim that people would act more negatively.