any market can be manipulated. The financial market it's self is pretty decentralized (even more then bitcoin). If you think of it over 50% of the BTC mining market is in china and is controlled by 4 organizations. What financial market in the world is more at the whim of so few people?
That wouldn't give Chinese miners control over the
market. All miners can do is add (or shut down) hash power, order transactions into blocks, and sell block rewards on the market. Miners do not control the supply. Like any "whales" in the market, they can only sell for so long before their supply is distributed (if the intention is to suppress the price).
The "4 organizations" bit is misleading too. Just because a pool possesses hash power at this moment doesn't mean it owns the mining hardware. We have no idea how distributed mining power is. At the drop of a dime, a lot of mining power pointing at Chinese pools could be pointed elsewhere.