I disagree with china can determine the fate of bitcoin. There is a large user population outside of china. China has banned and unbanned bitcoin more than I can follow. Bitcoin kept plugging down the road, china can do what they want it wont affect the long term viability of bitcoin
But it is the fact that China currently controls the majority of hashes although it's far from 51% attack it could be a problem later on. However, if China really does harsh law enforcement regarding cryptocurrencies or even banned it with punishment for those who break the law. We could potentially lose a major hashes power However it will then adjust automatically after 2016 blocks and become profitable again for small miners to mine bitcoin. Actually there's nothing really need to worry about as of now and to be clear, China didn't control Bitcoin but a price manipulation with massive capital could still happen.