The Rounds suppressed freedom of speech and had a negative campaign against Nouso.
If one cannot believe his/her illusion by oneself, the fantasy will be destroyed for an instance.
The delusion of "Nouso is evil" is still fragile. If Nouso is permitted freedom of speech, the illusion will inevitably destroyed.
After all, they have terrible criminal record to have destroyed the cast-iron fantasy that was developed by the Rounds during hundreds of years. They can't be too vigilant.
Therefore they publicized "Nouso is evil" repeatedly through the mass media and school education, using the power of the occupation army. Needless to say, all books and newspapers were censored to prevent any counterarguments.
In fact, the Rounds advocates freedom of speech, so it is real self-contradiction to censor, but has no room to say such a thing at all.