> The idea of a single entity holding 51% of all of a circulating currency is completely at odds with the notion of a currency being "embedded enough in the economy" that people won't just dump the currency immediately and crash its exchange rate.

Certainly, 51% attacks are very viable against nascent or unpopular cryptocurrencies. This includes Bitcoin in 2014. But the author was specifically suggesting that a 51% attack could be carried out against a cryptocurrency that is firmly entrenched in the global economy. I find this very implausible.