I think that's where the real hornet's nest gets stirred up....
And I think that the majority of people in the field would agree that a lot of earlier science-fiction, and even of those works that were the precursors to sf, should still be considered such with the caveat that
they were within the bounds with the scientific (or, in some cases, pseudoscientific)
understanding of their time, but that our information has now superceded that. I don't know how many on here are aware of it, but until around the late 1930s, and even well into the 1950s, science fiction was considered to be a branch of fantasy. (I make the qualification because some of the fans began to differentiate it from outright fantasy without any scientific element about the 1930s, but it was a slow process, and even many of the best editors in the field continued to consider them part of the same thing until well into the 1950s.) (How's that for throwing a spanner into the works of this discussion -- even my own comments?)
However -- I think that the majority (based upon the various arguments I've seen, and the various statements by writers and editors and sf historians and critics alike) would come down in favor of the system I note above: Let the older entries in the field maintain their status with that caveat; but for newer things they must be much more stringent on their application of the word "science" because it has become so differentiated from fantasy
per se. (And, just for the record, I'd class the Back to the Future films as definitely fantasy with scientific trappings but no science; i.e., science fantasy the same as Moorcock's Eternal Champion, several pieces by Ellison, etc.)
Also, just so I'm clear on this ... I tend toward the older idea myself; that's a definite shift for me, as I began by reading sf considerably more than fantasy; but as I learned more about the history of the field, the more I began to see that the older classification makes a lot more sense, and gets rid of the whole conception that because the science in a story is no longer valid, the story isn't valid -- which is utter nonsense. If the story itself is well done, it is still a good
story, no matter
how erroneous the science is.