None of your points are relevant to the concern that the military presence was meant to stifle American's ability to exercise their first amendment right to protest. The United States is not China. The threat of a few extremists committing violence is not a reason to prevent Americans from voicing their concerns. The Chinese government used the actions of a few violent extremists many years ago to suppress the rights of their citizens, including the right to privacy, and to think freely (the violent extremists have been used as the basis for sending millions of minorities to concentration/reeducation camps).