The difference is that communists accept the need for censorship and are open about why some ideas need to be suppressed.
Because some ideas are so destructive to your whole model that they have to be suppressed, because these models in their practical application are often sort of un-defendable, and so the only option is to have secret police running around shooting dissidents.
It doesn't mean that liberal democracies don't fall into the exact same pattern, to some extent large or small. It is in the nature of human power struggle. It's not innate to any particular political system (or it is innate to all of them because they're all made of people). The difference is that we don't celebrate it or make excuses for it. We publish books about what a lie the government is telling, we have a constant struggle between the forces of freedom in the streets and the government trying to stamp it out. Sometimes different factions get the upper hand, or it switches.
The difference, as you brilliantly demonstrated here, is that some of the most thickheaded of communist supporters get themselves turned around sufficiently that they start supporting the government trying to stamp it out. Most sensible people, when the government tells them that some ideas need to be suppressed, and they need to imprison or shoot anyone who's opposing their power, can figure out that's a bad thing. You apparently cannot.