"Human beings don't serve any useful function in space," Weinberg told SPACE.com. "They radiate heat, they're very expensive to keep alive and unlike robotic missions, they have a natural desire to come back, so that anything involving human beings is enormously expensive."In addition to addressing the practicalities of spaceflight, he takes on the misplaced priorities that has often accompanied NASA due to its goals of manned spaceflight:
Here is the response of the National Space Society, an organization dedicated to promoting the spread of humanity into space. To counter the manned spaceflight program being a waste of money, they list a number of technologies that were developed due to manned spaceflight, "...such as kidney dialysis machines, fetal heart monitors, programmable heart pacemakers, to name just a few that help Americans every day."
Weinberg pointed to NASA's treatment of its Beyond Einstein program as an example of the agency's misplaced priorities. Beyond Einstein consists of five proposed space missions designed to build upon and expand Albert Einstein's General Theory of Relativity.
"Only one of them is slated to go ahead, and given NASA's record, if we suddenly run into extra expenses in the manned spaceflight program, that will be put on the back burner, just as has been done time and time again by NASA," Weinberg said.
And they continue on to show that both theoretical physics and manned spaceflight have both done good to humanity, and it wouldn't be fair or wise to scrap one for the other. I'd recommend reading them both.