The problem with the argument is it always ends up circular to some extent. I always see something like the below - where crypto enthusiasts always try to argue bitcoin is something different than the current argument being levied against it...

Crypto Enthusiast: "Bitcoin is a currency"

Crypto Sceptic: "Well it's not a very good currency because of X, Y & Z reasons, and nobody is spending it"

Crypto Enthusiast: "Well it's not really a currency, you need to treat it as a precious metal"

Crypto Sceptic: "But precious metals have intrinsic value - ultimately you can make something from them"

Crypto Enthusiast: "Well it's more like you can make sure your money grows rather than being shrunk through inflation - look how it's always growing!"

Crypto Sceptic: "But isn't the growth just driven by pure speculation? As in price increases just come from new people entering crypto at the bottom, and pushing it up to people who bought it earlier, who have an incentive to promote it? A bit like a ponzi scheme? I mean nobody is spending it so if it's not growing what's the point?"

Crypto Enthusiast: "Well if it stops growing that's fine because it's really a currency"