Holden implicitly questions the ethics of his brother's decision to become a Hollywood screen-writer instead of a writer of literature. Holden's old English teacher, Mr. Antolini also comments on this subject, suggesting that a person with talents like D.B.'s should not be allowed to write movies. 

Another sublte moral question the book brings up relates to Holden and his compulsive opinions. Is a person as flawed and unstable as Holden really a in a position to judge others on the grounds of integrity?

The treatment of other people is a moral/ ethical concern that is brought out in the text.  Of specific note would be whether or not it is morally correct for Holden to condemn most of society as being "phonies" and inauthentic.  There is an ethical dimension to which Holden carries himself, one that reflects a judgment of people even before they have an opportunity to demonstrate whether or not they fulfill the tenets of that judgment. The manner in which Holden treats people or deals with them is of ethical concern because it is not reciprocal. His hatred of social conformity, the world at Pencey Prep, and the people which he meets all receive his quick judgment, one that does not necessarily embrace a full ethical consideration of human judgment.  To a great extent, Holden does not appreciate the way in which the world dismisses him, so the ethical question is begged of whether or not Holden can treat others in the same manner.  In this light, there is a "Golden Rule" issue in play in that Holden struggles with treating people as he, himself, would want to be treated.  I think that the treatment of individuals is an ethical concern that is explored in the text.