Who am I to say? What do I know? As you might gather from the name Graybeard in the blog title, I'm an old guy. The word Silicon reflects the fact that I made my living in silicon - I'm an electrical engineer. When you've flown someplace, whether large jet or smaller plane, chances are your life depended on my designs. I'm also a member of what we usually call gun culture 2.0, and have trained myself to use machine tools passably - well enough to make guns out of aluminum and steel from the raw stock.
You see, this isn't about the second amendment or about guns per se; this is about first amendment-protected freedom of speech. It's just that the speech is specific directions for someone with savant syndrome (a handy mental model for programming a machine) Like the stereotype of someone with savant syndrome, the computer (in this case, built into a 3D printer) is pretty useless, but like the savant, it's really good at one or two tasks.
We have over 200 years of legal precedent that it isn't permissible to prohibit the printing of anything, no matter how distasteful you might think it is, and there is solid precedent that computer code is included under the first amendment.
Your "downloadable death" phrase is a nice, catchy, phrase, but like most such advertising slogans has little do with reality. Your breathless description in the CNN op ed might possibly be as much as half true. It is certainly full of exaggeration. You say,
Imagine this: the convicted domestic abuser next door tries to buy a gun. He’s turned down because he fails his background check. When he gets home, he opens up his browser, and in half an hour he’s printing out his own undetectable, fully functional plastic gun, with no background check and no record of his purchase.First, these guns are not trivially easy to make. On typical low-end, home printers, they'll take over a day or two of printing. They don't come off the printer ready to use. A lot of parts have to be printed, the finish work done on those parts, and they have to be assembled properly. Second, these guns are not "undetectable" because they have metal parts inside. As you might think, plastic just isn't strong enough for some things and metal is needed for some components. Plus, an old law on the books requires all guns to be detectable by airport security-level devices, practically stating that they need some metal in them. You might call Cody Wilson a lot of things, but "stupid" isn't a word you would use; Cody made sure that the otherwise plastic Liberator contained enough metal to comply with the Undetectable Firearms Act.
As for "no background check and no record of his purchase", that's no different from how the majority of guns used in crimes are obtained. They're not bought by law-abiding people who then go wild. They're either stolen, or bought from someone who stole the gun. A recent study in Chicago said the typical criminal was never more than 3 acquaintances from a gun. Your hypothetical "convicted domestic abuser" can get a gun cheaper and with less effort that way than getting a printer.
The picture you chose to Tweet is particularly dishonest and deceptive. You tweeted a picture of a solid metal gun printed by a high end (half million dollar) metal printer. Would anyone in their right mind buy a half million dollar printer to print a gun they can buy on the corner for a hundred bucks or two? Again, the parts coming off a 3D metal printer also require finishing and assembling, so 3D printing metal guns is a circus trick. It can be done, but that's just to show you can do it. It's economically stupid.
No, this is about the ability to disseminate knowledge as computer code and the constitutional protection of things people are uncomfortable with. Have you ever heard of the Anarchist Cookbook, Alyssa? This book has been continuously available in the US since the early 1970s and includes information on making bombs, horrible poisons like ricin, other weapons, and even drugs like LSD. You can buy a more recent, more "sanitized" version of it right now from Amazon, or you can download the original 1971 version from several places online. The point is this is protected free speech and our society has a couple of hundred years of precedent that we allow people to say what they want, even if we abhor it. In fact, we allow it especially if we abhor it. Offensive speech is the only kind that needs protection. If we all agree with it, there's no controversy.