Weyoun: "If you ask me, the key to holding the Federation is Earth ... our first step will be to eradicate its population. It's the only way."
And there's your justification.Fans (some) also or instead read it as at the end of the day there is a Federation with a massive civilian population that absolutely has to be protected. And that this is the number one ethical imperative.
If your moral position is that it better to die to the last man, woman and child rather than violate some ethereal principle then I submit that you're placing priorities in the incorrect order.
Since total victory is to all intents impossible, crushing your enemies rather than making actual peace will always lead to circular repeated conflict. If it is right to crush an opressor, to then oppress it in punishment, then you continue that pattern...those former opressors become the oppressed, and will of course then turn around and crush those that crush them (see twentieth century history, and in a less violent way, the current political shifts happening) If the federation ceases to be the federation by rejecting its values, what has been preserved? It is still lost. The federation has to 'win' to preserve itself physically, but it has to win in a way which retains its identity to preserve itself ideologically...which is is ultimately what the federation is, an ideology, not anything approaching a nation state.....which is ultimately what it does, and ultimately what Ds9 is actually about, even In The Pale Moonlight. For certain conflicts, fought on ideological lines, you cannot reject your own ideology in order to 'win'. The entire Dominion war is not about destruction....the Dominion wants to rule, not destroy, but Dominion rule would destroy and go against the ideals of the federation. So they cannot abandon those ideals without in fact losing the 'moral high ground'. It would cease to be something like a 'Just' war, and simply become about who has more power, and using that power as a 'right'.
Is my moral position to die to the last man? No. But it would be to know, really know, why I would be fighting. Though let's be honest....both sides in any given conflict will consider themselves to be 'right' and 'just' and it's only when you get down to something like an objective viewpoint that judgement can actually be made....even war has rules, and from a human perspective there are some things that are just so wrong that they needs must be fought. But never lose sight of what you are fighting for, never simply replace one oppression with another, if you actually want anything approaching peace. History is full of groups who, having decided they had 'won' against some terrible evil, then forget the how or the why, and fall into another form of oppression, sowing the seeds of their own future enemy. Every empire in history has done this in some way, from Pre-History to the current failings of the Post Cold War set up, even on a simpler cultural and political basis without delving into warfare. And people who say the same stuff I just did probably turn up, and sometimes while societies aim for being magnanimous is victory, and create a peace for a time, sooner or later...the same mistakes are made, and the whole bloody wheel starts turning again. Which is rather crap for those of us out the edge of the wheel. Those comfy in the centre just get a little dizzy. Then of course you can get jaded and cynical about ideals, and then the only right becomes the right of the strongest and most powerful with some force, military, economic, cultural, it doesn't matter. And guess what. You have an opressor again. Which will create its own Nemesis...and...well...you get the idea.
And that is why, within the fiction of Star Trek, the Federation cannot allow something like S31. Because then the Federation is not the Federation, and is no longer particularly culturally distinct from Romulans or Cardassians. The Klingons become the good guys by default. And our 'heroes' know that, even Sisko after his brushes with journeying down that dark path.
