Quote 28
"Art has no influence upon action. It annihilates the desire to act. It is superbly sterile. The books that the world calls immoral are books that show the world its own shame. That is all." (19.10)
This idea of art simply revealing what's already wrong in the world echoes Lord Henry and Dorian's excuses for their sins – the idea that sin is latent even in the innocent person.
Quote 29
Yet it was watching him, with its beautiful marred face and its cruel smile. Its bright hair gleamed in the early sunlight. Its blue eyes met his own. A sense of infinite pity, not for himself, but for the painted image of himself, came over him. It had altered already, and would alter more. Its gold would wither into grey. Its red and white roses would die. For every sin that he committed, a stain would fleck and wreck its fairness. But he would not sin. The picture, changed or unchanged, would be to him the visible emblem of conscience. He would resist temptation. He would not see Lord Henry any more -- would not, at any rate, listen to those subtle poisonous theories that in Basil Hallward's garden had first stirred within him the passion for impossible things. He would go back to Sibyl Vane, make her amends, marry her, try to love her again. Yes, it was his duty to do so. She must have suffered more than he had. Poor child! He had been selfish and cruel to her. The fascination that she had exercised over him would return. They would be happy together. His life with her would be beautiful and pure. (7.33)
At this important turning point, Dorian consciously decides that he will try and halt the downward slide of his soul. He realizes belatedly the value of his prior innocence, and of Sibyl's, and vows to attempt to return to that state.
Quote 30
Every moment of his lonely childhood came back to him as he looked round. He recalled the stainless purity of his boyish life, and it seemed horrible to him that it was here the fatal portrait was to be hidden away. How little he had thought, in those dead days, of all that was in store for him! (10.12)
The idea that the rotten portrait should dwell among the trappings of Dorian's destroyed innocence disturbs him. We feel a tinge of regret, or something like it, emanating from our protagonist.