Censorship is often made to hide things for the wrong reasons. Censorship on bombmaking might be a valid reason according to some. But most censorship has nothing to do with information that's dangerous in that way. Censorship is there to protect very few people, often to the disadvantage of a larger group. See china.
But there's nothing inherently bad about censorship if it was an open and voluntary process where a democratic society voted to ban bomb making plans or something.
Though it throws into question what right the mass has to control these people. What if you censored every LGBT person, they couldn't comment on youtube. Is that justifiable? Same goes for most other things, why should bomb making enthusiasts be silenced when it's the perpetrators of terrorist actions that commit the crimes (before there's censor laws anyway).
But that has less to do with censorship and more to do with other liberties. In general it can be said that it's rarely for your (most peoples) benefit. So it's inherently bad in a democracy. Compromises (exceptions) are often made today though, even in some of the most liberal nations.
