Musk's rather immature remark shows why we can't trust profit-driven billionaires with our future in space. He is clearly trying to suck up to the Trump administration in the hopes that any space weapons programs resulting from the Space Force will mean new launch contracts for Space X. As any Star Trek fan knows, Starfleet's primary mandate is space exploration--'to seek out new worlds and new civilizations, to boldly go where no one has gone before'. It is more like NASA than Trump's Space Force. It is the product of a world in which human-against-human war has been abolished, and humanity turns its energies outward into the galaxy. Of course, many central aspects of Star Trek (such as a galaxy chock full of improbably anthropomorphic aliens) aren't scientifically plausible, but it does represent an important cultural metaphor for a positive space-faring future, which is why Musk's remarks are distressing.
At the beginning of the space age, president Eisenhower, concerned about the growing power of the military-industrial complex, wisely placed control of our space program in the hands of the civilian NASA. He sought to limit military space efforts to matters such as reconnaissance and communication. Today, the United States and many other countries are heavily dependent on satellites for their military and civilian infrastructure. A space arms race, which the Space Force makes more likely, would place all of those assets at risk. The simplest way to protect them is a treaty banning space weapons. Space weapons might make military contractors even richer, but they won't make anybody more secure. Besides putting our satellites at risk, such programs will suck resources away from the sort of exploratory ventures that Star Trek symbolizes, and will poison the Star Trek-style international cooperation needed to make them happen, though it may give Musk big contracts for hauling weapons into orbit. Trump seeks to supplant Eisenhower's wisdom with his own incompetence. Before taking office Trump remarked that he eagerly sought an arms race because he thought the United States would win. 'We will outmatch them at every pass and outlast them all", he said. No one "wins" an arms race, all sides lose-- and risk doing so catastrophically. All of this is about deadly serious global security issues, not "sweet spaceships and pretty good uniforms and stuff". Sorry, Elon, but this is the kind of irresponsible thinking that will make the world into a post-apocalyptic wasteland, not a Star Trek-style techno-utopia. Grow up.