However it is a fact that what he says about China controlling Bitcoin mining and this having potentially very negative impacts.
China controlling Bitcoin mining is not an argument. China is 20% of the population, not surprising that China outnumbers here. One could claim that Bitcoin is completely centralized because Earth controls 100% of its hashing power.
If what you wrote were logical, then decentralization would always be the same as centralization.
Decentralization is where the decision making power is spread out to as many actors as possible. A few miners in China making the decisions for all the users of Bitcoin, is not decentralization. You are conceptually conflating the sham of representative democracy (or in this case
taxation without representation because we don't even get the illusion of voting) with decentralization.