Censorship; where does the first amendment end and censorship begin?

There are several groups out there, on Facebook, which are offensive of the highest nature. Is just one of many pages that have received notice for offending or upsetting someone? There is a petition to fire Bill Maher, and another to deport Piers Morgan. This brings us to the million dollar question, when is it okay to use censorship? What about books that contain offensive and graphic information, should they be censored? There is a lot of questionable material out there, and so we are faced with a big question of whether censorship is appropriate.

A couple years back there was a college professor who wanted certain books banned from a local middle school. Two of the books were directed at young readers and while they both discussed the idea of sex, neither went into any great detail. The third book, was far more questionable in nature as it discussed illegal drug use, sex, and violence in every gory detail. Regardless of the books though, the same question is posed is censorship alright? Do we censor books that have offensive material and who makes that decision?

I am offended by certain language, and certain activities, this same language and activities are not offensive to you, do we censor? What about this page? That could be considered highly offensive, especially to Jewish People, Christians, and others with good taste. Still the question remains, where do we draw the standard? What is appropriate for everyone? Where is that invisible line in the sand? I think it is safe to say that Child Pornography is wrong, inappropriate and should be prevented at all costs. At the same time, I am sure there is someone out there who would make the argument that I am wrong. Do we draw the line on censorship at child pornography, or pornography of any kind? Do we draw the line at sexual scenes in movies and books? Where do we make the distinction that something should be censored? Where does the first amendment end and censorship begin?