The Police of London actively scan and monitor social networks looking for “hate speech” so they can pursue legal action. What’s the difference between that and what China does?
https://gking.harvard.edu/publications/how-censorship-china-...
Directly inciting actual physical violence, you might have an argument for.
But words and ideas must remain free to maintain any semblance of a free society.
As other commenters have said: who decides?