I read through a lot of comments here but didn't see this thought yet, so I apologize if it's a repeat:
This ruling means that there is no such thing as free speech anymore. The first amendment is null and void. Why? Because if something becomes illegal to say on the basis of "national defense", then the government just needs to define more and more things [that they don't like] as a danger to national security/defense. That line is arbitrary, and the courts seem to always agree with the Executive and/or Legislative branch when they place something in the national security bucket.
If SCOTUS doesn't overturn this, then the day will come when speaking in a way that disagrees with the President will land you in jail because the Federal Government will have defined that as treachery and a clear danger to the security of the State. You see, what you said "is not merely tangentially related to national defense and national security; it lies squarely within that interest."
The whole freaking point of the 1st Amendment was to have the right to say things that the Government squarely disagrees with. If we've lost that, this country is legitimately doomed.