I see your point. It is essentially that my argument is a slippery slope if I say speculative fiction is too divorced from reality.

However, I generally reject slippery slope arguments on the grounds (pun intended) that perspective is still important. Fiction has been an important part of helping people to feel a personal connection to distant or remote events from the dawn of recorded history. No one asks, for example, if a man was really attacked on the road from Jerusalem to Jericho and then helped only by a Samaritan, who stopped to help when no one else would. In fact, we assume the story is not true, but it represents a moral idea that has been so powerful that the "Good Samaritan" is almost a cliche phrase in our society.

However, the more elements of the unreal you introduce into a story, the more likely the audience is going to be distracted by that or find reasons to discount the moral you're trying to impart. To take an example that I (with regret at this point) used in my original post, the story in Eternal Sunshine of the Spotless Mind does not require the audience to believe too much that is fanciful. The only fanciful element is a technology that does not exist and that is explained in a very simple manner. If the audience accepts that one little deviance from the world they understand themselves to be living in, the story works.

If, however, that story were in space, it requires people to believe that the future will be as depicted. If various types of aliens exist, it then asks the audience to accept that various types of aliens are zooming around the stars as we speak. More and more of your audience is lost with each step.

That having been said, I do think people should read non-fiction as well. I read non-fiction on a regular basis (in most years, I read as much non-fiction as I read fiction, if not more). Last year I read 24 non-fiction works and 15 works of fiction (I removed the Bhagavad Gita re-read and reading of books of the Bible in the original languages from that list before counting). This year, I read 20 non-fiction works and 19 works of fiction (again, discounting books that are considered sacred texts, but not discounting commentaries on the same).