Isn't that the same argument used by China for why the GFW is needed? The US allows all sorts of things that can be argued as net negative (e.g. smoking).

It is not. But not banning it for geopolitical reasons is a net positive for everyone.

It is a net negative.

Attempts at intervention by legacy states over the evolution of the internet (which will obviously fail on sufficiently long time-scales) are also a net negative.

Two net negatives do not make a net positive.