In China, the level of trust people have in the Government is very high compared to the US and Europe. That is the reason why this policy would work and would have reasonable public support.
In the US or Europe, a policy that seems reasonable but could be exploited by the Government for political control is a bad policy. In China, people have already sort of accepted that the Government is pretty secure in its position so it really doesn't need to suppress speech in roundabout ways; if the intention is to suppress speech then they will be explicit about it by using the words "this threatens state security" or "this is offensive to public morals". The thing about being a secure authoritarian regime with reasonable popular support is that you don't need to come up with pretexts to suppress speech or dissent. You can just say "this threatens our power" and put a stop to it. If the policy states the goal is to stop uninformed people from spewing nonsense on the Internet then people will accept that to be true, and the reality is that it probably is what the goal is.