Giving weak arguments does not demonstrate that one is not arguing honestly and in good faith; only that one has cognitive limitations, or blind spots, or something of the sort. Which, alas, we all have here and there, and it's hardly astonishing if a religious person has them in areas closely related to his religion.

(That might, for present purposes, be functionally equivalent to not arguing honestly and in good faith, and I share the suspicion that CSL wouldn't be likely to be deconverted after an hour's discussion. But it's not the same thing, and in particular doesn't have the same implications for the person's character generally.)