Corey's post suggested that literature itself is a vehicle for moral agency, with which minorities can express their perspectives and experiences. I agree with this; when members of a minority group write, they increase the knowledge, sympathy, or even empathy a reader has of this group. This change in knowledge and emotion is very likely to change (for the better) how readers act toward this group.
I would caution, though, about the work of minority writers being defined by the author's status as a minority. When, for example, an Asian-American female becomes a distinguished author, critics always bring attention her status as a female and as an Asian-American, and seem to segregate her work into its own category and to place it only among other literature of Asian-American females.
I do not think that society should define members of minority groups by their minority status. A good work of literature should be (excuse the tautology) a good work of literature; not merely a good work of Asian-American, female literature.
