Arms=small arms and nuclear arms.
It's interesting that you're willing to draw lines with regard to free speech, but incapable of drawing lines with regard to second amendment arms. Like it or not, semi-automatic handguns and long rifles are within the bounds of the second amendment. Nuclear arms are not. The second amendment does not support your supposed line drawing against machine-printed semi-automatic guns and gun components.
Free speech famously has limits (falsely yelling "fire" in a crowded theater) so where do we draw the line here?
That old saw does not cut it. The pro-censorship crowd famoulsy assume that a line must exist for any given situation, and then seek to draw it wherever is necessary to achieve their goals. What is false in the digital files describing how to manufacture a machine-printed semi-automatic handgun? Nothing. You want to censor true speech. Trotting out a rhetorical flourish concerning false speech does nothing but demonstrate that you have no sound basis for suppressing true speech.
Whatever line may exist is far, far behind you.
"Suppression of speech as an effective police measure is an old, old device, outlawed by our Constitution." - William O. Douglas, Watts v. United States, 394 U.S. 705 (1969).