Are you interpreting "down on cryptocurrencies" to mean "in favour of cryptocurrencies"? I think GP meant the opposite.
I have a low opinion about the usefulness of cryptocurrencies because true security is so difficult. It's basically impossible, even if you don't make any mistakes.
I really enjoy this kind of stuff, and loved reading about the z-cash ceremony. I'm not going to those lengths to protect my secrets, so I feel it's better if I don't hold a lot of wealth in such a fragile way.
I used to like it, but now I don't. It's still neat, but it's too prone to costly mistakes.
[1] https://www.nerdwallet.com/article/investing/bullish-vs-bear...
not everyone is a stock marketeer - I personally keep reading bullish as derived from a bully - something clearly negative