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William Shatner: ‘Good science fiction is humanity, moved into a different milieu’
(www.theguardian.com)
Based solely on that quote, I whole heartedly agree. Science fiction is almost always supposed to expose something about our world through a different lens. Whilst it's not the most elegant example, the two black & white striped races in TOS arguing over "black-white stripes vs white-black stripes" was a clear allegory for racism in our country when the show came out. District 9 is a decent allegory for something like Gaza & Israel: open air prisons and what-not.
Science fiction should (IMO) make the muddy waters of morality more clear.
A more nuanced example comes from Battlestar Galactica; wherein the human members of a concentration camp use suicide bombing as a means of rebellion. The show made sure to imply the efficacy of suicide bombing. It also made sure to expose the arguments against it. But I think during a post 9/11 world, suicide bombing was looked at as the root of all evil. Perpetrators were seen as aimless villains without a cause or reason (without a rational one, anyways). But BSG did make a compelling argument for such extreme cases of terrorist violence when your back is up against the wall.
The bajorans in DS9 also make cases for terrorism as an act of rebellion against colonizers.
I think science fiction is one of the only genres they really take a look at these topics. Other genres seem to only gleam the very tips of the morality iceberg.