Your critical responses focus on parsing the meaning of "astronaut," or on the true utility of the job with respect to other non-human test pilots.

I leave all of that aside, and agree with you on egalitarian and emotional grounds. The term in America rightly has implications of public service - of deserving the fantastically unique opportunity of exploring space on behalf of all Americans by virtue of intelligence, diligence, and impeccable ethics. Topically, this might be compared to Olympians: though all extreme athletes perform extraordinary feats, Olympians carry an extra responsibility to represent us as a nation. So too with people called "astronauts."

Whether or not one agrees with this understanding, I believe it is the practical understanding underlying your (and my) insult at the use of this term.