His PhD was about environmental damage in China. That is not something cultural or diplomatic. It does not require close ties with China, though it does help to have access.
Nothing here means you shouldn't criticize China. In fact, the premise of the research becomes moot if you cannot criticize China.
it evidently is or else we wouldn't be having this discussion right now. Everything in China is political which everyone knows who has ever interacted with Chinese institutions. (which you probably will if you study environmental damage in China).
It's really not that surprising that a professor is not going to associate with someone who posts vaguely racist cartoons to his ten followers on twitter if it costs them their visa.
If you really want a career that involves studying aspects of a foreign culture you better learn to navigate the waters or you won't have a career, that's not really a new thing. If you're an archaeologist you probably won't be one for long if you insult the governments that let you access your dig sites, is that really a scandal?
I think it actually requires both diplomacy and cultural awareness.
If you want to study the ‘damage’ that a country is doing, it seems like it would serve you well to avoid ruffling too many feathers so that you can do your work in peace and without being accused of bias.
Nothing here means you shouldn't criticize China. In fact, the premise of the research becomes moot if you cannot criticize China.