What event causes Steven to change his mind about the Pure Movement in the novel, Vox?

Steven really embraces the Pure Movement when he is recruited to serve as a volunteer to teach the younger girls about the movement. Steven demonstrates his faith in the movement and its leaders when he turns in his girlfriend after she initiates a make-out session that leads to sex. Because premarital sex is illegal, Julia is arrested. Steven is deeply upset when he sees how disrespectfully Julia is treated not only by the leaders of the Pure Movement by also by his teacher and fellow classmates. Steven demonstrates that he has learned that the Pure Movement is not as ideal as he once believed when he goes to find Julia, supposedly with the hope that he can do something to help her.