This one's pretty simple: China is a totalitarian regime that is in direct conflict with western constitutional values. So if influence is aimed at democratic foundations, of course it's a bad thing.
I don't see why those principles should apply to a foreign country with malign intentions, they aren't a person nor do they represent a populace given that China is authoritarian.
The spying seems secondary to the influence they can wield by pushing certain stories while burying others.
Not in principle. Practically all democratic systems have provisions to defend against subversion of their core principles. Those provisions may be designed to safeguard institutions, processes such as elections and regulate information flow.
It's important to remember that the US concept of "free speech" as an absolute right is very untypical, and that it also has limits due to being narrow in its scope.
Of course, banning a social network due to arbitrary or without reasons would be against democratic principles. But following democratic and legal principles to openly apply laws and procedures designed to safeguard the state - that's not undermining at all, to the contrary!
Collapse of Polish–Lithuanian Commonwealth in XVIII as form of proto-democracy can be here good case study. It show us how authoritarian systems can exploit democratic system.
