Actually, the comment you're referring to just suggests people take a step back from the material of the letter, and look at its overall effect: one of self-aggrandizement.

Once you see that, the material of the letter takes on a different aspect. Even if it weren't from a psychopath, it would be enlightening.

(I have other issues with your use of naive logic based on non-probabilistic propositions, but you may be doing that to dumb it down for the audience.)