What do you mean by “randomly feels like it”? Maybe he wants some fresh air or something… Then it’s a personal motivation, and my answer is (d) not relevant to ethic. The discussion in this article was not, I think, about casual goals like climbing a mountain, but about the goals in your life, the important things to do (maybe I should use the term “finalities” instead). It was a matter of ethic.
If Bob believes that climbing this mountain is good or important while he admits that his only motivation is “randomly feeling like it”, then I call his belief absurd.
I wonder if the same mechanisms could be invovled in conspiracy theorists. Their way of thinking seems very similar. I also suspect a reinforcement mechanism: it becomes more and more difficult for the subject to deny his own beliefs, as it would require abandonning large parts of his present (and coherent) belief system, leaving him with almost nothing left.
This could explain why patients are reluctant to accept alternative versions afterwards (such as “you have a brain damage”).