How can you actually shut down mining? Maybe they'd make it harder for miners to convert bitcoins to fiat, but that wouldn't stop the mining.
But I think the parent's point was that, if the Chinese exchanges were shut down, that could have a big impact on price if the hypothesis is true that most bitcoin activity is evading Chinese capital controls. If the hit was big enough it might push mining into unprofitability. This is all speculation, but not impossible.
Also, what would happen to all the mining equipment should a mining farm get shut down? If the shut down is permanent, you can bet the people that own those machines would try to sell those miners as quickly as possible to people outside the country that can run them.
The economic incentives of bitcoin are such that there will be significant resistance to any government attempts at shutting down.
I do agree though that shutting down the larger Chinese mines wouldn't be too difficult if the government had the will to do it.
You may not be able to shutdown mining, per se, but if you are the PRC government, you may be able to isolate miners in China from the network (especially if it is important enough to you to accept false positives), which has the same pragmatic effect.