Why is it offensive?
In the blog post the author mentions that a number of the people who have attempted to censor The Catcher in the Rye did so because they disliked the world Holden lives in. But, of course, if the censors had actually read the novel, they would understand why the novel is the way it is.
As a number of scholars have pointed out, censors tried to ban the novel for its inclusion of the “F word,” as if the novel would spread indecency, even though the whole point of including the word was to show how Holden Caulfield hated that the word was graffitied on walls where children could see it. The word evokes the sense of disgust Holden feels toward the way the modern world ruins the innocence of little kids; ironically, to censor the word would be to shield the reader from acknowledging how ugly the world can be. So, Salinger included it.
I think the post was written for those people who refuse to read any dark fiction, and, more importantly, consider reading unsettling texts like The Catcher in the Rye antithetical to being a good Christian.