The response in the interview mistakes the nature of the original question. Not every meaningful statement exists on a binary truth spectrum. Not every meaningful statement corresponds to a claim of empirical fact with quantifiable uncertainty. Saying "I have complete confidence in someone" is not a probabilistic assertion akin to saying "I am 100% certain it will rain tomorrow." Rather, it's an expression of trust, commitment, or endorsement—often used in a social or political context to convey support, leadership assurance, or accountability.
Confidence i...
As a moderator of /r/TheMotte (back when it was on Reddit), I recognize that username immediately. He was tempbanned a few times (largely for those sorts of posts), but at the same time he was featured well over a dozen times in the "Quality Contributions" post we had to highlight the most informative/thoughtful posts. Just as a bit of a balanced perspective. Not to defend him entirely, though, I personally view his tantrum after being called out for plagiarism to be quite an indictment on his character, however insightful his blog posts are.