Mutually Assured Destruction assumes both sides has about equal destructive ability.
As for hashing power, it is clearly in the favor of China.
If China destroyed all foreign use of BTC though power plays or etc, they would be
making BTC as worthless even to themselves.
If this was their plan, it would have been smarter to wait till it became the
"world's currency" before playing power games. "It's the slow knife...".
LOL,
They devalue the Yuan all of the time, their people still use it.
BTC would be no different.
They had to tip their hand to keep their 51% control, allowing the updates would have removed their dominance.

We are way offtopic so I'm not going to continue from here,
but your opinion is incorrect. Their people are forced to use it like all national currencies.
BTC is a threat to the Chinese Communist System. If you think they will use BTC as their
main currency you obviously don't know the Chinese government.
FYI:
You freely admit they control BTC and have the power to pull off a 51% attack.
But you want to pretend that they will never use it. With 51% China has absolute power over BTC transactions.
"Power tends to corrupt, and absolute power corrupts absolutely.
China controls more hash from LTC than they do with BTC, why are you supporting that coin more?
Your crazy, the Chinese financial systems and government love gold more than anything.
They will never allow Gold/BTC exchanges. If they do, they aren't the masters, but the pawns.