The actual suggestions from the paper in question:
Here we suggest two concrete ideas for government officials attempting to fashion a response to such theories.
First, responding to more rather than fewer conspiracy theories has a kind of synergy benefit: it reduces the legitimating effect of responding to any one of them, because it dilutes the contrast with unrebutted theories.
Second, we suggest a distinctive tactic for breaking up the hard core of extremists who supply conspiracy theories: cognitive infiltration of extremist groups, whereby government agents or their allies (acting either virtually or in real space, and either openly or anonymously) will undermine the crippled epistemology of those who subscribe to such theories. They do so by planting doubts about the theories and stylized facts that circulate within such groups, thereby introducing beneficial cognitive diversity.
“The hardcore conspiracy theorists are totally committed. They’d have to repudiate much of their life identity in order not to accept some of that stuff.~Zelikow quoted in the paper in question
I may be wrong.
Here Sunstein clearly expresses the notion that he can conceive of a scenario where the government might indeed feel compelled to consider a ban. You can try to run interference for Sunstein if you want, but there is no place for him to hide. It is there in black and white.We could imagine circumstances in which a conspiracy theory became so pervasive, and so dangerous, that censorship would be thinkable.