I love this statement:
A textbook based on a community perspective valuing audience and ethics would begin much differently [than textbooks that start with “Writing is an important means of expressing yourself”]. Maybe like this: “You have a duty and an obligation to write, not because you have ‘the truth’ and must share it with others, but because we need to discover truths and we need all the help we can get, yours included. You write because you have an obligation to do so. (Porter 123, emphasis in original)
Porter, James E. Audience and Rhetoric: An Archaeological Composition of the Discourse Community. Englewood Cliffs, NJ: Prentice Hall, 1992.