It's true. A government can only censor so much content. Inevitably there will be some escaping it.
But if everyone censors themselves out of fear, then that's much more effective of a power for a government to have, since they barely have to do any censorship work themselves. They just need to set examples every now and then to remind people "what's waiting for them" if they dare try to expose the truth.
I've said it before around here - the most dangerous thing is not the dictator himself. He can be removed if, and only if, the population itself has a free spirit and viciously opposes him, until they remove him.
But the real threat is when part of the population starts believing in the dictator's "ideals" and principles, and defend his actions "for the good of the people", and the other part is too scared to say anything anymore. That's when a dictator can rule in "peace", for a long time, and so will his successors, because then, for "his kind", the environment is very "welcoming".
Here's a good example of the opposite of self-censorship, and what everyone should be doing: