A strawman is when you make up an argument to defeat it. She has made nothing up, the reviewer said, "As Le Guin isn’t a hard science fiction writer, these traits aren’t technological — technology is carefully avoided — but philosophical, psychological, social, or linguistic." You can complain that the reviewer is wrong in their characterization of hard science fiction, but Le Guin is not beating up a straw man, she's responding to an argument that she disagrees with, explaining her disagreement.

The straw man was the 2 obvious statements she made (sci-fi has more than science, technology is more than computers and whatever). She argues for both, when nobody was arguing against, then says; therefore I write (hard?) sci-fi.