You seem to imply that this is some metaphysical discussion on the nature of "truth" itself or who gets to be the arbiter of that - but I feel this is a dishonest digression here. Yes, truth can never be truly established - but both you and I know that Chamath's take on All-In for this particular claim was clearly false.
I agree with the poster you replied to. I guess you have a point in that there is no law that can tell Chamath to shut up and only open his mouth when he is talking about something with high confidence - but when you are speaking to a large audience on matters of economic policy with some implications as to what people believe then YES - you have a responsibility! The punishment to which breaking it should be (for people with a huge outreach like Chamath) being shamed online for it. People should learn the fact that Chamath is a man who chronically opines constantly about things he has no basis for having an opinion on. He is a chronic borderline liar.