Let's assume a scenario in which there is a large violent anti-governmental protest in the United States against the killing of Qasem Soleimani. The protesters manages to raise $70 million, without the permission from the authorities. Now the authorities order the bank to freeze these funds. Do you think that the banks will be in a position to reject the directive from the authorities?
If there is a legal order coming from the courts, then the directive will be followed by the banks. Otherwise, the government cannot just command any bank for that matter to freeze a particular account simply because it is used for non-violent protests, or owned by some opposition groups of members, etc.
Hong Kong is a very rich financial district not just within the Chinese territory but the whole of Asia. There must be so many business tycoons inside and outside Hong Kong who are one with the objective of the protesters which is to maintain their state's freedom against the authoritarian hands of China.