Why do people hate censorship?

I'd tell you, but I'm not allowed! Seriously, censorship limits what people have to say, treats people like they are stupid, and stifles the flow of communication.

Sure, there is a lot of things out there that probably should be banned. But is this a good precedent to set? Obviously, we should ban things like child pornography, but a sliding slope can set in. If child porn should be banned, why not things that tell people how to commit crimes? But one problem is, what you think should be a crime might not be what I think should be a crime. One person may think that homosexuality and all literature related to it should be illegal, and another may want to ban the materials belonging to a rival religion. Yet another may want to ban scientific theories or political speech they disagree with. Hate crimes laws are being used to go after more than just hate crimes. They also censor hate speech, and a problem is that anybody can decide that more and more things are hate speech.

Even if you decide that some things should be censored, then there is the problem that it isn't an effective approach to reducing the spread of the content. If you say something should be censored, others will only want to see it more. They may want to see what makes it so bad. Those who want to see such things will only set up secret societies to get to use them without regards to the laws.