Well, it's not too different from all the things other governments do while killing net neutrality. DPI, adding advertisement is also a way of modifying content. Just China blocks certain services completely. The tech itself, peeking into packets, finding out what they are about to manipulate or block them is something also ISPs in many western countries, like the US do.

Coming from Europe I was fairly surprised how often both injecting data into traffic or blocking ports is. Also here they say it's for protection. I wouldn't point to China.

About what can be done. There actually many projects on decentralizing the internet, making it more resistant to single points of control and even making censorship hard or close to impossible.

Netsukuku, cjdns, B.A.T.M.A.N. and others are big steps into the right direction, but it even seems like the urge isn't big enough. They don't get lots of interest, donations, etc.

This is a very important point. I honestly don't know what can be done about this, but I hope this is on the radar of any country that cares about freedom of expression for all people regardless of their country of domicile.