The Confederate flag has different meanings to different people however.

Sure. But I'd have to hear what the "meaning" is supposed to be and why it is so closely attached to the military colors of a long-dead slave empire. Certainly the historical reasons why the flag is a live and potent symbol for some of my fellow Southern whites (I was raised in eastern Alabama and live there now) seem to me to have a lot more to do with the legacy of white supremacy than not. When white people tell me that they are flying that flag because they want to invoke some kind of "Southern heritage" or "Southern identity," it seems to me that they have a pretty curiously selective picture of just what they are inheriting and identifying with. (It doesn't seem to have much to do with the legacies of Southerners like Harriet Tubman, or Ida Wells, or Rosa Parks. Which I guess is not surprising, since none of them would be much interested in having the Battle Flag as the symbol of their legacy....)

Meaning in any case is not just a purely private affair -- whatever the "intent" behind the flag, it does also matter how other people will take what you do.

The semiotic intent of painting the stars and bars on the Gen. Lee--
that famous car from the 70's hit tv show The Dukes of Hazard-- surely
was not to celebrate a slave empire?

I dunno; I expect that the idea was to celebrate "the South." But the idea of "the South" that is defined by the Battle Flag and by the hero-worship of a statist slaving warrior like Robert E. Lee is not an entirely separate thing from the celebration of the Lost Cause. Certainly whatever meaning was intended, it doesn't seem to be a meaning that leaves very much room for the lives or heritage of many Southerners, most notably those who happen to be a bit blacker than the Dukes are.

I don't think Sergio said anything about how awful America is as a country, compared to other countries. Why do you keep trying to make this into some kind of race to see who is the "best" or the "worst"?

His point was that the standards you endorse with regard to killing Koreans for the crimes of "their" government abroad would also seem to justify killing Americans for the crimes of "their" government abroad.  This has nothing to do with comparative judgments of better or worse; it has to do with applying the same standards for guilt and punishment across the board. Sergio's point is that regardless of how comparatively awesome or awful a
government may be, when you line it up next to the other governments, the question is whether the people of the various countries that have to endure any of those governments are, or are not, the people who ought to be punished or killed for the evil or aggression of the governments that dominate them. And if you don't like what your stated standards for answering that question would recommend with regard to American civilians, then perhaps you also ought to reconsider applying them to Korean civilians, too.

You say it is "an appalling travesty of conscience" to take millions of
N. Korean lives if necessary to prevent the missile launch in my
scenario, but it is not apparently "an appaling travesty of conscience"
to do nothing and let millions of innocent American die. I don't see the
logic of this.

Because I don't think that "millions of people are going to die either way" is a good reason to conclude "So I may as well pull the trigger myself; at least that way I get to choose the ones to die." If you think that (1) being forced to watch millions of innocent people die, and (2) actually going out and killing millions of innocent people yourself are exactly the same from the standpoint of conscience, then I'm not sure I know what to say to that.

But of course in any case I didn't say that you should "do nothing." I said that the things you do need to be limited to things you can do without massacreing millions of innocent people. Perhaps you think that this leaves nothing at all to do, but I don't. (*) Even if it did, though, see above.

If put to this choice, I believe the inherent right of self-defense applies.

I agree with you that people have a right to self-defense and that it applies in a situation like this. But I don't agree that its application encompasses killing unrelated third parties who aren't threatening you. You can defend yourself by killing a person who threatens your life. Not by killing his neighbors until he stops threatening you.

It is similar in my view to the defense of "necessity" under the
criminal law. If a person puts a gun to your head and says he will kill
you if you don't kill another innocent person, if you pull the trigger
the defense doesn't work. Even if you are an innocent victim, you got
yourself into the situation and can't kill someone else to get yourself
out.

O.K. But it seems to me that that position bolsters my case more than it bolsters yours. I'm not the one trying to defend pulling the trigger on innocent bystanders here; you are. My statements about Korean victims of the North Korean government had nothing to do with a "necessity" defense -- there's no defense to be made because the millions of Korean civilians that would be killed didn't shoot or bomb anybody in the first place. They need no necessity defense because they didn't do the deed to begin with. Whereas when you propose having the U.S. government pull the trigger on millions of innocent Koreans, your justification is -- as far as I can tell; correct me if I'm wrong -- that they had to do this because somebody else -- to wit, the North Korean government -- is holding a bomb over the heads of innocent Americans, and the only way they or we can get out of that is to kill someone else. Well, maybe so. But you just denied that anyone has a right to save their own skin at the cost of innocent third parties' lives.

If those living under extreme despots know that they will not suffer
the consequences of aggression by their leaders because they are
innocent bystanders, they don't have much incentive to rebel, do they?

Seriously? Suppose that someone (let's name him "Osama bin Laden," after no-one in particular) were trying to justify massacres of American civilians as retaliation for U.S. foreign policy, and he made an argument like this:  "If those living under the American government know that they won't suffer the consequences of aggression by their leaders, they don't have much incentive to rebel, do they?" Well, actually the U.S. government gives Americans plenty of reasons of their own to rebel, and the North Korean government gives Koreans even more. (They haven't succeeded at that yet, but that's because a rebellion against an entrenched regime is a hard thing to pull off, not because people aren't sufficiently motivated.) But even if they had no reasons at all to rebel, that's not a justification for massacreing civilians until they have been properly "incentivized."

The reason is that those civilians' lives are not geopolitical bargaining chips to be bet and lost. Their lives are their own. They are not yours to sacrifice for a desired political outcome, or to bargain or to trade off for the well-being or even the lives of people that you know and like better.

(*) If you had -- ex hypothesi -- certain knowledge of a pending attack, you
might start by sharing this knowledge with others, so that people in the
line of fire might have some chance of getting away from known or likely targets.

is back in Alabama