Those violence is indeed not acceptable. However, proclaiming all pro-Chinese students behave / think the same way is also too subjective or even racist in some extreme cases.
If the Chinese students have a different opinion, they should do the same thing as the HK students. They can also start a petition / protest to against violence riot in their Country.
Free speech is not only available to HK students but to Chinese students in Australia too. The principal of free speech is not just speaking out loud without any responsibility, it's about mutual respect.
A side note is that although you may feel insecure / anxious about being monitored, it is not necessary the fact without any evidences. As a free country, anyone can feel whatever they feel like. With the same theory as one of the HK student, others with opposite opinion can feel that they will be assaulted in HK given the violent riot situation in HK too. If that is the case, free speech is not being taken away by the Chinese government but by the rioters themselves.
If the Chinese student assault HK student, he should be put under the justice system. If HK police is using excess force, they should be put under justice system. If HK rioters broke the law, they should be put under justice system. Denial should never be excuses for act of violence.