Why would anyone publicly known for criticising the Chinese government, especially someone of Chinese ancestry, even go near China itself? Even a layman is aware they don't give a toss about 'rules' when it comes to suppressing perceived enemies and moreso when the person involved is of Chinese ancestry. The Chinese government has made very clear that anyone of Chinese ancestry is under their control and owes allegiance whether they think they do or not. Only us dumb Westerners apparently think citizenship isn't tied to race.
If this guy wanted to try his luck, he also picked the wrong passport. A US passport might have given him a bit more leverage here not to mention (again) I find it hard to believe he isn't aware of the massive penetration of Australian society, politics and the economy by Chinese influence in recent years. I'm surprised at this point his case has even been raised with the Chinese government.