Where does a writers responsibility begin and end?

Following my post on Fifty Shades of Grey, and the white hot rage it and it's message inspired within me, not to mention arguments such as racefail (which still has cause to rear it's ugly head from time to time) and this recent article in the Guardian, I've been thinking a lot recently about a writers responsibilities.

There isn't a lot of fiction out there that elevates any minority to positions of equality. Those that do exist are most often found within the realm of science fiction and fantasy, though there are equally as many fantastic universes created which still seek to oppress minorities, seeming to long for the good old days, when women were little more than princess in ivory towers and slavery was normal.

Any media can be a force for change, putting forward points of view that make us stop and questions ourselves and our preconceptions. Star Trek having a black woman on the bridge, for example, was unthinkable in the 60's. Of course the majority of telephone operators in a telephone exchange were women, so perhaps making her the communications officer was not that ground breaking after all. It made a bold leap, no doubt, but was that leap bold enough? Why couldn't Spock, the second in command, have been a woman, or heaven forbid, even the captain! Even just making a woman the navigation officer would have been better, and at least then the Enterprise would stop and ask for directions when needed!