Marketing books and "author brands" (read: authors themselves) really can be a tricky business. You have a platform, and you have fans, which means people pay attention to what you say. You are, to a greater or lesser extent depending on the size of your audience, under a microscope. Whatever you say and wherever you say it, you can rest assured that it is recorded for posterity and will likely be shared at some point.
Many authors--most of them, even--tend to stay away from controversy. They don't talk politics, art, or religion. They keep their opinions to themselves because they don't want to alienate a single reader. They want to be judged on their books, not on their personal views.
And that's fine.
There are notable exceptions, though. Stephen King makes no secret of his political views. Hell, he named his kid Joe Hill. I get the impression that his opinions on social issues haven't changed much since he was a wee lad, and he expresses them with admirable eloquence. Has this ever hurt his book sales? I doubt it. By the time we lived in this media-everywhere world, his books were well familiar to readers, his brand firmly established. It certainly strengthened my King faniness. Would the Tea Party take him on? Well, they have yet to do so (to the best of my knowledge), so probably not.
There's another author whose political views are so repugnant to me that I will never purchase a book he's so much as breathed near. I've gone so far as to rearrange store shelves to make his books less visible. My opinions aside, though, his books sell. Still, I wouldn't like to try to market them.
When Allendegate broke (you knew I was going to mention it, right?) some authors, including Charlaine Harris, Mark Billingham, and Val McDermid, jumped in quite publicly. Others were vocal about it in social media venues. We found a wonderful spokesperson and advocate in McKenna Jordan of Murder By the Book. Most authors, though, stayed mum. Given some of the backlash I experienced for expressing strong opinions on the matter, it's hard to blame them.
Still other celebrity authors use their personal politics as some kind of bizarre performance art. James Ellroy is the best example. Whatever he's doing doesn't appeal to me personally, and makes me glad I don't like his books (I know, I know, shut up), but it seems to get him attention among the devoted particularly.
I was pleased a couple of weeks ago to see Margaret Maron supporting Clay Aiken's congressional campaign. Pleased, because I agree with her political views, and she obviously cares a great deal about her home state. Did she offend some (potential) readers? Maybe. But it was obviously a risk she was willing to take. It made this reader more likely to seek out her next book, though.
So where does this leave us? Should authors express opinions on controversial issues? On art and politics? As with most things, there's no one right answer. Most crime fiction includes some element of right vs. wrong, of good and evil, and as such, chances are good that your sense of justice and morality are already on view. Because reading is an intensely personal experience, we tend to feel like we know authors through your fiction. If you choose to talk about this stuff, you're inviting readers to agree or disagree with you personally, and possibly shattering their construct of you, which is a risky proposition.
On the other hand, if you feel strongly about something and you speak about in a way that's as unlikely as possible to incite offense, you might just find your loyalty quotient with readers rising.