Here, Wilde challenges what is considered "good" or "bad" literature by claiming that books, poems, or other forms of art should be judged on its writing. Thus, regardless of Dorian Gray's homoerotic undertones, Wilde's prose evokes deep emotion and, because of that, the novel should be considered "well written." Additionally, through this quote, Wilde calls out the critics who have defined his art as immoral or "bad" because of perceived obscenities and failed to judge the text itself. In Wilde's first response to St. James's Gazette, he claimed the following: "My story is an essay on decorative art. It reacts against the crude brutality of plain realism. It is poisonous if you like, but you cannot deny that it is also perfect, and perfectionism, is what we artists aim at." As a whole, the preface seems to emphasize that rebuttal, but it is especially prominent here.
From DUGGAN 63: After further discourse on the novel, Wilde himself admits, in a letter to the St. James’s Gazette, that Dorian Gray “is a story with a moral. And the moral is this: All excess, as well as all renunciation, brings its own punishment." Aestheticism does well to condemn the renunciation of desires, but it is an excessive obedience to
these desires that is subversively dangerous. Therefore, in the practice of Wilde’s aestheticism, forethought and constraint are necessities, yet too often lacking, and without them, one is doomed to suffer the same fate as Dorian Gray.
Also, Wilde's phrasing that "there is no such thing as a moral book" sent Christians into an uproar, for the basis of their faith is based on a holy, moral book: the Bible. Christians believed that Wilde, in saying this, was practically denouncing Christian religion.