There are some mostly untrue assertions on the essay. Most cryptocurrencies are not fungible. Cryptocurrencies are not taxed at large YET, but they will. Most cryptocurrencies in use today are extremely volatile, so they can be used by speculative investors, but right now, they are very risky as stores of value.
That said, I believe cryptocurrencies are the future of money, as those issues are resolved by better technology and new cryptocurrencies, just it might not be the ones existing today, especially not BTC.