I think that the point Kenrick is making is that in the sci-fi genre there is science fiction and then there is science fantasy.
Science fiction is less forgiving from a tech point of view and most of the concepts can be rationalized from today's understanding of technology.
Science fantasy is the opposite and often these advanced pieces of technology that can not be rationalized in any way from a technological stand point.
Now IMO the most important aspect of all of this is the basic idea that this is fiction which is defined as "storytelling of imagined events" by Wikipedia. This makes the debate about the practical use of railguns as a hand held weapon seem, for lack of a better word, silly. The entire idea is to dream up new bits of hi-tech gadgets, not provide the technical specifications so that the US government can go out and equip all of our troops with it tomorrow. Just my 2.5 cents.
And to think that this whole topic actually started with a question of who would win in a fight between the Battlefield: Evolution USMC (set roughly ten years from now) and bugs...