As much as its fashionable to hate on China and its government, it's important to understand that Foreign government social manipulation of citizen and instigate chaos is real and it's not limited to US or western countries or only through the internet. As someone who owns and runs an ISP, I see governments in many countries, through my peers in the industry, (including developed, developing and poor countries), go through great lengths to tighten the screws on the internet in their respective countries. While very few countries do it as intrusively as China - most countries do it at some intrusive degrees, with laws and regulations.
Political destabilizing through the internet is a real thing and has been for many years and as more companies rely heavily on the internet for their business - stability of the internet infrastructure is very much tied to individual countries economic health and faith.
Does China go too far in regulating their internet?
Most probably yes.
Is China's internet policy completely unreasonable on unfounded security grounds?
Abso-fucking-lutely not.
The problem is no one really knows what the middle ground between the openness of the internet and policing it just the right amount. So we end up with an extreme case like China.