>But if you are in position to launch the counterattack(say sitting in a missile silo with your hand on the launch button), then once the missiles are on their way to you, you are dead.

Can you explain why you think this is relevant? Military/security personnel accepting their own deaths as part of winning is hardly some alien concept. If you're sitting in a missile silo ready to launch then you will have gone through a lot of training (and/or indoctrination), mental prep, and practice for the event that is hoped to never come and knowing that if it does your life will be one of many gone. In fact, even for civilians if you're guaranteed to be dead anyway but have a few minutes left to make a difference, that could just as easily trigger a "well, might as well spend whatever I've got left trying to take the enemy with me and ensure my side still has a chance" mindset.

Also, thinking out the implications of your argument the moral position appears dubious in other ways. For example, it suggests that it'd be preferable to initiate a first strike, and wipe out all those millions, if you knew that would save your own hide and side vs a second strike after already being attacked in the hope of helping others beyond yourself. And if not that then it ends up "well I wouldn't push it no matter what", in which case you wouldn't be there right? And what if it's not "millions" in for your launch? You need to define how many it's ok to kill, like if your particular silo is aimed at military targets, other silos out in the middle of nowhere. Or does your argument boil down to total pacifism?

>And yes, it might improve the chances of the survivors, but at the same time, you know that if you press that button millions of people will die.

Millions of people will die anyway. Millions of your people. Whereas the millions (or hundreds/dozens, see above, many missiles aren't aimed at cities) you kill by pushing the button will be the millions who were on the side that killed your millions and may well be reasonably expected to then come and finish the job for your millions of survivors [1]. Remember, the argument here is whether there is a rational position in favor of launching. Many debates have multiple fully rational but conflicting positions, nothing wrong with that! But that doesn't mean they aren't all rational in and of themselves.

You can certainly hold the moral position that every life is valuable and that leaving the enemy, no matter how horrid, to profit from mass nuclear attack and take over the world is the right thing to do anyway. I'm just saying that such a position is not the only rational one at all.

>I think I'd just leave it at that point.

I think you wouldn't pass screening to be put into that position in the first place, even assuming you volunteered for it which it doesn't sound like you would. I can't say I'd want to be in that position either, though at the same time I want to be cognizant of my shared responsibility for it as a citizen.

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1: At least for America, most of the population is urban, but with a total of over 320 million that still leaves a lot of people in rural areas. Specifically (based on the last census numbers I found) about 97% of the land area of 3.8 million mi^2 is classified as "rural", and it contains about 19% of the population (so about 60 million people). Even in the case of all urban centers being destroyed that's still a lot of people left in absolute terms. It is for example more people than the total national population for the first century of the country's existence (up until around 1890).