Why not ban gold as an investment too? It's just as much a zero sum game or gambling if you wanna call it that. Also a lot of resources wasted in storing it in bank vaults just sitting there for nothing.
You're just avoiding saying gold has value. Why are you avoiding saying that? Because then you have to make it clear that value is determined by people and people have deemed crypto valuable, especially Bitcoin. Your implied argument is, when explicit, more clearly vacuous.
Perhaps his point is that the minimum value of a physical entity like gold is greater than $0, but I see your point/criticism too. Essentially "define value" can lead to varied definitions?