If someone is saying a lie they should not get away with it. They're doing it deliberately to hurt someone's reputation. On the other hand, though, is it a lie or do they believe it? That's another thing one has to prove. But if it's harsh criticism, yeah that person is a jerk, but it's the truth as well (though they could have said it in a less as-holish way), so they can't be punished for that.
There are many arguments that favor censorship, and one of the biggest one has to be from the Chinese Government. They claim that by censoring China they are saving and protecting the heritage and purity of the country as by not letting western influences influence them. They claim that by doing so China will one day rise to the top and be the most powerful of all people.
Yes, there are arguments in favor of censorship. Even if these arguments are quite stupid, there are still a lot of people who are arguing for it. Especially people in congress. Our rights to free speech are slowly being widdled away a little bit at a time, and censorship is another step in that direction.