Hi, all
First of all, this video was amazing and very insightful. Of course, I have my own interpretation of it, so I will not claim a privileged perspective. I interpreted it as dealing more with epistemology rather than other branches of philosophical thinking like theories about the truth (although they are interrelated). Probably a good idea would be to define what we mean when we say that someone is wrong about something. Although the most common response would state that someone is wrong when that person believes something that is not the case, I think we don't gain much with this idea when we apply it to deep disagreements. For example, political or moral disagreements.
I would say that someone is wrong regarding a moral or political stance when that person holds a belief without being justified, irrespective of the belief.