If I don't believe I am right, or at least making an important point (such as playing devil's advocate), I'm doubtful that my comments are relevant or helpful in figuring out what is true.

It may be worthwhile to consider the role of curiosity and questions.

By contrast, your interpretation of the quote suggests that Professor Armstrong should be indifferent to whether particular x-risks that he has highlighted as "most dangerous" are actually the most dangerous x-risks.

The first interpretation sees 'right' and 'wrong' as the property of people, not ideas. Doing so is less helpful than seeing rightness as a property of ideas- the plain truth.

Thus, it suggests that the Professor should be indifferent to which x-risks he highlights as most dangerous, except for the criterion of danger. It would risk sorting his list incorrectly to confine himself by his opinion, his past statements on the issue, or those which avoid giving support to an enemy.

I agree that your third suggested reading is not a very interesting assertion.

I was introduced to the poem by someone who was arguing against moralistic thinking, who knows much more about this sort of poetry than I do; I mention it for completeness, as it may have been the author's preferred interpretation.