This is why we can't have nice things.
Small-scale manufacturing is the source of all coming nice things. Yes, yes, you can use it to make guns - or anything else for that matter! 3D printing will never, by itself, make Star Trek replicators a reality, you need both additive printing and milling to make small-scale, eventually in-every-home, manufacturing a reality. The "Ghost Gunner" is just an ordinary CNC mini-mill. That's kind of the point here: it's not a tool for making guns, it's just a tool. And a damn impressive one.
Yesterday I had a crown put in. The last crown I had took 2 dentist visits, because the crown had to be manufactured in a lab and mailed, a multi-day process. Yesterday it took under 2 hours. The dentists scanned my tooth, designed the replacement on a computer as I watched, and (with some intermediate steps) it was automatically milled in a back room while I waited. We're living in the future, and, yes, the future will have guns, which even if you think that's a bad thing, just think of all the other stuff we'll be making ourselves, or in the office of the appropriate professional.