When Udo Schuklenk and I put together 50 Voices of Disbelief: Why We Are Atheists, we had no trouble finding people from the science fiction community who were enthusiastic about the project. If there's ever a sequel, we'll find others of equal stature. (It's also true that many or most mainstream authors are atheists, or at least not conventionally religious, but in my experience it is considerably more difficult to find mainstream authors who are prepared to give priority to public criticism of religion.)
The author of this anti-sf screed, apparently one David Cloud, laments that, Science fiction takes the reader into a strange world without God. Oh, there might be "a god," a "force," but it is definitely not the God of the Bible, and the prominent names in this field are atheists. He concludes: Science fiction is intimately associated with Darwinian evolution. Sagan and Asimov, for example, were prominent evolutionary scientists. Sci-fi arose in the late 19th and early 20th century as a product of an evolutionary worldview that denies the Almighty Creator. In fact, evolution IS the pre-eminent science fiction. Beware!
Leave aside the fact that Sagan and Asimov were not evolutionary scientists - Sagan was an astronomer/astrophysicist and Asimov a biochemist rather than an evolutionary biologist. It's true that science fiction arose in response to developments in science and technology, but not just to the theory of biological evolution.
Most of the article is devoted to listing various people who were famously associated with sf, with brief descriptions to warn us of their godless ways. For example, Robert A. Heinlein is described as follows: Consider ROBERT HEINLEIN, called “the dean of science fiction writers.” He rejected the Bible and promoted "free sex." His book "Stranger in a Strange Land" is considered "the unofficial bible of the hippie movement." Heinlein was a nudist and practiced "polyandry." He promoted agnosticism in his sci-fi books.
This is all slightly odd, particularly the bit about "polyandry" - I don't think the author knows what this word means. I suspect he's looking for the word "polyamory". Still, it's not wildly wrong: Stranger in a Stranger Land was, indeed, a kind of bible for the hippie movement, and somewhat beyond that; and it remains influential on many people for its critique of monogamy (among other things).
Mr Cloud gets nuances wrong throughout, but his overall message of warning is not crazy if you buy into his fundamentalist religiosity in the first place. If you are a Young Earth Creationist and a supporter of religious sexual morality, science fiction is not going to be for you. By its nature, science fiction promotes rational thought and subverts traditional religious worldviews. To understand this, we should see science fiction as a cultural phenomenon produced by distinctive historical circumstances.
Even before the era of modern technoscience, human societies had, of course, always experienced change - from wars, famines, and plagues, for example - but the idea of future societies with radically different social and economic organisation was probably unthinkable before the seventeenth and eighteenth centuries, while the transformation of societies by the irreversible advance of technology became apparent only in the nineteenth (see Robert Scholes's excellent little book, Structural Fabulation, for more on this). For the first time, it became possible to think of a future greatly different from the present as a result of continuing changes in technology and scientifically-based knowledge. As science began to investigate the very small, the very distant, and the long history of the world and its many forms of life, a new understanding of the cosmos emerged during the seventeenth, eighteenth and nineteenth centuries. By the end of the eighteenth century, scientists were starting to describe the extreme vastness of space and the astonishing depth of time. A far more precise understanding of the magnitudes involved was worked out through the twentieth century and up to the present day.
Thus, humanity's understanding of its own place in the cosmos altered drastically over a period of just a few hundred years. Homo sapiens came to be understood as a product of vast space and deep time, a species with an evolutionary origin and a psychological nature honed by millions of years of Darwinian adaptation. Nothing in this picture refers to a god, let alone to humanity as the focus of a god's concern. Though the scientific picture of the cosmos remains incomplete, much of it is now well-evidenced and too robust for any reversal to be imagined. The basic propositions of biological evolution, for example, are now so well-supported by evidence that they should be accepted as facts.
The scientific picture destroys old concepts of human exceptionalism, while offering marvels more astonishing (if less intuitive to beings like us) than anything found in pre-scientific mythmaking. Thus, the last few centuries - since Galileo, say - have seen a breakthrough in conceptualising the cosmos, the past, the future, and ourselves. This has offered new opportunities for storytelling.
During the nineteenth century, imaginative writers increasingly speculated about technological devices not yet invented; conceived of diverse possible futures; or filled the immense universe, the imaginary future, and the deep past with exotic locations for tales of adventure and heroism. As the pace of social, scientific, and technological change accelerated during the twentieth century, narratives of technological innovation and futuristic prospects became even more culturally prominent. Science fiction, as the emerging genre came to be known in the 1930s, expanded into new media such as radio, cinema, comics, and television.
That does not mean that science fiction is monolithic in its attitudes to science and technology. While science fiction gives at least nominal assent to the emerging scientific picture off the cosmos, the scientific picture is often presented in a greatly distorted and simplified form. Furthermore, although typical science fiction narratives raise questions about the effects of technological development on individual humans and human society, some are far more optimistic than others. Many sf authors evidently see technoscience as a blessing, many others as a curse. Optimists imagine the development of a more mature, less warlike, humanity, the wise integration of technoscience into society, and expansion into space. Pessimists emphasise the dangers of science and technology, often illustrated by narratives set in unpleasant future societies - and even more often dramatised by the rampages of new kinds of monsters (think, for a start, of Dr Frankenstein's creation, then track forward to the giant reptiles and insects of 1950s movies, and to the many science-based monsters of present-day sf).
With all these differences among individual works and authors, however, science fiction assumes, and thus promotes, the essential truth of the emerging scientific picture. It also assumes that human societies are open to change, including change in such things as religious beliefs. While there are narratives in which such institutions as the Roman Catholic Church prevail into the deep future, the general attitude to religion is a more anthropological one: the various future or alien religions depicted by science fiction writers are not affirmed as true, but are scrutinised for their wisdom or lack of it, used to drive the plot forward, or created simply to give extra depth and detail to fictional societies. The implicit message is that current religions are merely the mythologies of current societies, and they will not necessarily persist in times to come, even if something about human psychology drives us to create religion or myth of some kind or other.
It follows that science fiction really is dangerous from the viewpoint of religious fundamentalists, or even from that of a "moderate" religious person who sees her particular religion, claims about the supernatural and all, as actually true. Science fiction, even when it presents simplified, distorted, or laughably incorrect science, tends to undermine traditional religious pictures of the universe and our place in it. That, of course, need not be a bad thing!
Edited: to pick up a fair point made over at RichardDawkins.net.