Camera and Moral Imagination

Documentary is equally guilty of manipulating reality and privileging certain images, opinions and narratives over others. Still, documentary is often associated with its moral language. The audience of a documentary (rather than, for example, a fictional horror) are more likely to feel compelled to act in a certain way and to ethically respond to a situation. How can one reconcile the implicit manipulation of reality and the strong moral imperative that seem to coexist in a documentary?