This struck me. I don't think he was referring to some sort of cultural or societal obligation or expectation. It was more of a moral obligation that a writer should feel to tell the truth about the subject. I thought about this, and wondered if it could be taken a step further.
The historical and cultural value of writing is huge. We can study past civilizations and cultures through their writings. Through their writings, we can learn about how their society functioned and what their values were. In modern times, we learn through writings. We learn from reading the newspaper, novels, textbooks and (of course!) blogs. Perhaps some of the things that we learn from these sources are not "true" per se, in that the facts can be proven or disproven, but all of these writings serve as a way to hold our society together and advance as a civilization together.
So this led me to think about the responsibility of a writer to tell stories as they truly see it - without holding back. And the responsibility that you and I have to write, as much as we can. There is a distinct value in everything written, and it should not be discounted.