Here's an interview with Tim Powers in Strange Horizons. A lot of the discussion centers around whether or not writers should intentionally write with an agenda in mind:

Lyda Morehouse: You have suggested that certain reviewers have been taking an anti-Catholic view of your most recent book, Declare. Tell me more about that.

Tim Powers: Several reviewers and one judge for an award felt that the book was a pro-Catholic tract, I guess in the manner of C.S. Lewis's Out of the Silent Planet trilogy, in which Christianity is aggressively presented as true and important.

I love the Lewis trilogy, but I'd never write anything with a message, myself. I hate books in which the writer seemed to have "something to say." Ideally—and it seems in general to be the case—readers of my stuff should have no idea what my religion or politics are. I'm convinced that sneaking any kind of message into fiction makes cardboard metaphors out of the characters and the events (there are exceptions, as with the Lewis, but if I were to try it, it would not be an exception).

...

TM: I mean, what sort of statement can a writer make, in a story? "Racism is bad," "Sexism is bad," "Homophobia is bad." Well, sure—but a bumper sticker could have conveyed those, no need for a whole novel. And if you try to make a novel express these things, illustrate these things, it seems to me that the characters and settings and events just become jigsawed metaphor figures.

Here, of course, I disagree. I was thinking up to this point about novels like Lord of the Flies or 1984, which were obviously written with intentional message and metaphor...they weren't simply emergent effects of the author trying to tell a good story.

I simply don't think there's anything wrong with a writer trying to write a polemic in the form of a novel. Either they do it well or they don't. Similarly, there's nothing wrong with a writer who simply wants to spin a good yarn and get people to turn the pages...either they do this well, or they don't. Likely as not, if a writer is aiming for the latter, it is less likely that the work will turn out to be a great piece of art, though.

Because I happen to think that a great piece of art (great mind you, not just good), not only provokes emotion, heightens tension, suspends disbelief, and draws the reader in, but also informs some aspect of the human condition.

And contrary to what Powers says about bumper stickers, can you name me a great work of art whose theme could not be limited to a bumper sticker? Take anything written about war, for example. Most great works that deal with war could be simply reduced to "War is Absurd". Why waste all those other words?

Again, I think Powers himself is making some sort of judgement against writers whose focus is intentionally on theme. If his is on plot or character, and he does not want to consciously concentrate on theme, very well. That doesn't mean that a writer who does this is a hack. If they pull it off, it may very well be a great piece of art. If they fail, it will be very bad indeed. But so will a story in which plot and character were the focus, but were done very poorly.

And then Powers enters an area I obviously feel strongly about, as I've written about it here before. In the answer to a question about whether or not a writer has any moral obligations, he says:

So no, I don't think writers have any moral obligations when writing. All you can do is helplessly present your own core convictions, as illustrated in your (ideally unconsidered) selection of characters and problems and resolutions. Kingsley Amis wrote a couple of misogynistic novels, Lewis wrote pro-Christian novels and Pullman writes anti-Christian novels, James Branch Cabell's The High Place was believed to be a motivator in the Leopold-Loeb murders, Kipling and Lovecraft and Robert E. Howard probably wrote some "racism is good" stories—my own characters often drive cars while drunk!—but I don't think any of these would benefit by revisions to make them more moral, and I don't wish any of them hadn't been written.

Well, no, you don't just have to "helplessly present your own core convictions, as illustrated in your (ideally unconsidered) selection of characters and problems and resolutions." You could actually, you know, think about what you're writing and reflect on how your audience will react to it.

Powers has a couple of biases working here. One is that intentionally thinking about whatever moral or political issues your novel might deal with is going to spoil the art. The other seems to be that writing is more like a space capsule than a conversation. You just slap down on the page whatever comes out of your head and jettison it out there. What the public does with it is apparently none of your concern or responsibility.

I actually despise this mode of thought, and yet I hear it from artists time and again. It's one thing to say yes, I have a right to say something and I realize some people are going to interpret it in unintended ways, but it is an important story and one I both need and want to tell. That's different from not even considering how your story might affect others and absolving yourself of all responsibility.

Case in point, I remember attending the reading of Clarion instructor Suzy McKee Charnas' Hugo award winning short story "Boobs" when I attended Clarion in 2000. The story involves a teenage girl, a well-endowed outsider who is bullied at school, and who, upon getting her period begins to morph into a werewolf along with her monthly cycle. The story ends with her eviscerating the boy who bullied her, and with a suggestive quip that she might do it to another boy.

I remember being pulled into the story as Charnas read it, then recoiling from the subtext of the story once it was finished. Partly the story was about the awkwardness of puberty and the potentially traumatic transition from girlhood into womanhood. For this character, the beginning of menstruation actually shifts from making her feel like even more of an outsider to being an empowering event. But the way this is carried out in practice is that she murders, guts, and eats the person who is picking on her.

Now, as I sat there listening, I couldn't help remember the Columbine massacre, which had happened the summer before. You had misunderstood outsider teens who were bullied, and who decided to respond with violence.

If I were writing fiction for young adults, should I think about the theme of my writing? Should I at all care that I might be advocating particular points of view over others?

Do writers have any sort of moral obligation? Fuck yeah, they do. I'm not saying you shouldn't try to publish certain things because some people might be offended. I am saying, if you're not thinking about what you're putting down to paper and how it might affect others, than you are simply irresponsible.