You know , the space program was never all that peaceful to begin with... even if you leave the crazy plans like nuking the moon or packing AA cannons in space shuttles aside, to me it seemed kind of obvious that Russian and American interest in space was driven in no small measure because if you can make rockets drop robots and/or people in, say the moon, you probably can use that experience to make rockets drop more explody things on people you don't like.
That and, well, the fact that they were relying on the expertise of a nazi weapon designer
Flip that around. Rockets dropped explodey things first, then we realized we could use them for non-explodey things. Yes, the militaries of the world are already in space, and a lot of funding and resources for civilian stuff comes from military purposes. But so far those military purposes have been largely non-aggressive. And where they get most aggressive they stay covert about it which limits their effect. Recon, communications, navigation, that's all they really manage overtly. Stuff that we can all benefit from in some manner. Hell, the Hubble Space Telescope is a re purposed spy satellite. The space shuttle would have looked very different if the air force didn't have specific missions it wanted it to do in order to get their half of the funding in on it. So yes, civilian space benefits from the military.
But we also have this:
https://en.wikipedia.org/wiki/Outer_Space_TreatyIt's an old treaty, but it's still in effect. It doesn't necessarly ban the stationing of military units in space (except for WMDs). But it does ban stationing them on other planets and moons. Which means Trump's "Mars Awaits" patch could be indicative of ideas that would break that treaty.
Yes, the military has its influence in space. You can see it almost everywhere. But there's a line to be crossed from using space passively to assist earth based forces and putting forces into space ready to fight there. Fighting there is just not worth it. Nuclear weapons detonated in the upper atmosphere would ruin electronics, satellite AND ground based for 100s+ of miles. Conventional fighting which left debris would clog orbits and potentially set off
Kessler syndrome to ruin low earth orbit for EVERYONE for decades. And let's not even get started on the economic problems with an arms race if other countries decided they needed to stake their claim.
It's not worth it. It's dangerous. There's nothing to gain from it that we don't already have. And in my personal opinion, it's a pure ego boost move for Trump with little thinking actually involved.