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.
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.
Quote
"Power tends to corrupt, and absolute power corrupts absolutely.
FYI2:
What they could do is make BTC directly trade-able for gold in China only and it would stabilize it there, while they destroyed it in foreign countries.
http://www.bloomberg.com/news/articles/2015-04-20/mystery-of-china-s-gold-stash-may-soon-be-solved-as-imf-beckons
(Don't think they have not thought this thru.)
All of the rest of you are playing catch up on a Plan that was designed years in advance.