look...China knows they have already won.....on labor....they can't be touched....they have 300 million unemployed.....militarily....they can field an army of 300 million....they just need tech. for which the US will give away for money....... China just needs time to field a blue water navy which they are working on.... the China-Soviet-N. Korean alliance is being reborn....it just neeeds time.......
A fiduciary duty doesn't apply in a sense that you're implying when the counter-party is in violation of regulatory rules (ML is doing it right by alerting authorities and distancing itself from the hotcake). It is also different from the laywer-client confidentiality that you might be thinking about.
They also have a culture, like most of other countries, of "what is good for the many is more important than what is good for the few". If they freeze ML's assets, it would inconvenience thousands of Chinese customers. Would that be worth it in order to just say "tough luck US, your laws don't apply to us".