The real science done by Nasa has not involved humans. We have sent robots to places humans could never have survived and peered into the far depths of the cosmos, back to the early moments of the big bang, with instruments far more capable than our human senses, all for a fraction of what it costs to send a living, breathing person into Earth's orbit. The first rovers went to Mars for what it would cost to make a movie about sending Bruce Willis to Mars.
But science is not the real goal of human space travel. As I argued over a decade ago to the House Science Committee when Buzz Aldrin and I were asked to testify before their subcommittee on space exploration, we send humans into space for adventure. Astronauts inspire us by their courage and skill, and not least by the fact that they risk death every time they step into a spacecraft.
I personally have no problems with this fact. I believe the future of the human species will eventually be in space, and that we will one day colonise other planets. But we have to be honest about this goal.