I scrolled through the comments to see how many times this link will be posted, because this is the best answer to why censorship sucks, but somehow lack of censorship usually doesn't improve things.
However, sometimes I think that the concept of "web forum" is fundamentally broken, and need to be rethought properly, instead of making the same mistakes over and over again, because the whole thing is just incompatible with our instincts and needs.
Probably the greatest design mistake is having a front page that is shown by default to people who are not logged in. Because then it matters a lot what gets on this page and what does not. (Somewhere else in this thread people pointing at the front page of Voat. Somewhere else, people complaining about posts being removed from the front page of Reddit despite getting many votes by readers.) If you have one front page, there is going to be a war about what gets there. And the winner will most likely be a censor or a spammer; either someone with superior rights, or someone who dedicates most effort.
Compare with e.g. e-mail. You do not have one global front page of e-mail, so that people could become hysteric for there either being too much of X or not enough X. You have literal Nazis sending e-mails to other literal Nazis, and yet e-mail itself does not get the image of a "Nazi supporting technology". Probably also because other people's e-mails cannot be easily found and linked on Twitter.
Which leads me to another design mistake: making things public by default, as opposed to private by default. Public things can be linked, share, and wars started about them. What about having a limited exposure for everything instead? So that an anonymous user cannot see anything. Just like with e-mail. Just like with real life.
Why do people keep making these mistakes repeatedly? I believe it is because they optimize for profit through advertising, not for optimal debating experience. And making people yell at each other for 24 hours a day is the approach that maximizes ads shown.
But also users... they don't really want to be exposed to the worst parts of internet, and they don't really like the idea of being censored... but they like the possibility of being potentially read by tons of people... not realizing it means either online wars or censorship. It is hard to design a system that will show your content to uncensored masses, without something bad happening as a result. (But it isn't necessarily impossible. In real life, we have books that can reach millions, and yet the readers are not instantly interconnected with each other, or with the author.)
So I think the proper design should mimic these things from real life: talking to each other, debating in small groups, publishing books. No sharing. If I tell you something, you can quote me by copying my words (just like you can quote me in real life), but there is nothing in the software that will confirm that I truly said that. If I publish a book, you can't automatically find out who else is reading it; you can only ask the people you know, and they may deny it; even I cannot find out who read my book, unless people tell me. Probably a few more rules. In some sense, many of these are "anti-features" that prevent you from doing something that would start an avalanche.
Then you can have a platform with seven zillion witches, but as long as you do not add them as your friends, you will not be impacted by their existence. The only way to find out about their activity is to join them. The system is not optimizing for having you join as many debates as possible. It is the other way round: you need some of your friends to introduce you to the existence of witches, then you may ask to join them, then maybe they will accept you. Only then will the witchcraft content start appearing on your screen.