Chris Bowers makes the case for the space program. I don’t necessarily disagree that space exploration is a reasonable mission for the US government. But what was specifically at issue was manned space flight. There’s nothing categorically wrong with manned space flight — if we find something out there such that there’s reason to believe a manned visit would bring enormous benefits, why not send someone? — but at the moment manned space flight serves mostly as a costly distraction from more useful space missions.
Unmanned missions are, at the moment, the ones really pushing the frontiers of our knowledge and that’s going to continue to be the case for the foreseeable future. That’s where we ought to be focusing our energies. Meanwhile, we might want to offer encouragement and assistance to rising powers who haven’t yet undertaken substantial manned missions and for whom the “yes we can” factor still looms large. There’s nothing special about being the nth American in space, but the first Brazilian or Chinese or Indian mission to the Moon might be a big deal if one of those countries was so inclined.