Second, you're comparing the immediate, apparently permanent and total defeat of a Dementor to the warm-fuzzy feelings from religion, and you're also comparing the risk of Harry being wrong about the possibility of eliminating death to the risk of someone with strong religious beliefs neglecting proper medical care. Both comparisons are deeply flawed, due to substitution effects.
I'm not doing either of those things. I did refer you to a document that explains why the author of HP:MoR believes self delusion is a mistake when it comes to important beliefs. That document did include extreme examples to demonstrate the principle tangibly.
It sounds to me like you're just upset
I downvoted this. I am disagreeing with you because you are confused about what rational decisions are. I have explained the reasons.
that he used the wrong ritual but it worked anyway.
It didn't work. Nor did it fail - success or failure in defeating death hasn't happened yet. I have no reason to expect that self delusion would prevent Harry from killing a dementor, which is why I never suggested that it would.
That article was about doing things you know to be wrong, in pursuit of a flawed 'greater good.' The specific worst-case was believing something you know to be false. What knowably false belief are you saying Harry has accepted in the face of contravening evidence?
Update: This post has also been superseded - new comments belong in the latest thread.
The second thread has now also exceeded 500 comments, so after 42 chapters of MoR it's time for a new thread.
From the first thread: