If faced with a symmetric foe that has launched a nuclear holocaust upon my country, it would be absolutely essential to retaliate in kind so as to ensure that they could not mount a second assault and kill even more people. If I were president, I would not hesitate.
OK, and it's the end of the world as we know it. Like, Game Over, the survivors are back to the Stone Age and the civilization can start from scratch with 99% less people. Sounds like a sound decision you'd make.
It is ironic, but by taking a strong "We will strike back" stance, you decrease the chances of ever having to strike.
On the flip side, some of the well-trod ground is now out of date, too. Arguments about how maybe we could try non-proliferation instead become irrelevant as nuclear weapons become relatively speaking easier and easier to acquire due to advancing and dispersing technological sophistication.
Anyhow, upshot, if you're serious about thinking through the issues this turns out to be a really challenging stage to get up and morally preen at people on. It's very easy to end up advocating a strategy that kills billions of people while preening. It may be unpleasant to you, but you do in fact have to think. Hard. With neither rose-tinted glasses nor excessive cynicism. The easy answers don't work. The sweet answers don't work.
Indicating a willingness to use nuclear weapons at all may also make an adversary more willing to believe you may deviate from policy and strike first, which again may lead them to believe an all out first strike is safer than holding back (e.g. I've mentioned Able Archer 83, where the Soviet leadership allegedly considered a first strike because they thought the US was planning one)
Part of the problem is that neither you nor the other side knows whether your opponent will stick to any given strategy, nor if they will behave rationally.
The correct action may be to back down from a full scale launch while saying that you will respond in kind.
PS: South Africa actually gave up nuclear weapons. Which is the extreme end of not shooting back scale.
Advertising to the world that you have a firm policy against nuclear attacks other than in very limited, clearly defined scenarios puts you at risk of the other side decides it is ok to strike you for their own gains, but it also protects you against potential adversaries who have no designs on you but who you might inadvertently scare.
Able Archer 83, and the realisation that it appears to have genuinely terrified the Soviet leadership is often credited with changing Reagans course and making him determined to sit down with the Soviet leadership.
If your foe launches a strike that would kill 99% of the population of your country would you retaliate to ensure same level of destruction?
Now suppose you do also decide to retaliate to ensure 99% destruction to your foe. Would your foe's knowledge of that change whether your foe even tries an eliminating strike in the first place?
The same MAD principle? The knowledge that after 6 years, everybody will be exhausted by fighting, and what for exactly? Hitler wasn't rational, and maybe he would use nuclear weapons. Actors in the WWI thought it would last couple months, again, weren't exactly rational about what they are getting into.
It's not nuclear weapons what creates peace. It's the rational ability of humans to (eventually) see the hopelessness of destruction, that creates peace.
Whether the destruction comes from nuclear or normal weapons is irrelevant, however conventional weapons at least give us chance to have that rationalization later. In other words, stronger weapons require more responsible humans, not cause them to be more responsible.
The MAD doctrine is just a false rationalization of irrational fear. It is not a rational principle, it is principle adopted so that humans can feel better having nuclear weapons, although having them objectively makes the world a more dangerous place. If people indeed followed MAD doctrine as rigorously as MAD doctrine itself assumes, WWI and WWII would never have happened either.
In both of these scenarios if you are attacked first (early warning) your only option is to attack their centers of population to either prevent an all out invasion or to retaliate.
This is exactly why MAD sort of works, because it actually ensures mutual destruction of not only the nuclear and military capabilities but also of all national and human infrastructure as the only possible answer to even a limited nuclear first strike is "fire zee missiles!". Or to put it in a more structured manner there is virtually no room for proportionate response when it comes to a nuclear attack. When there was it was the biggest threat to "MAD" since it more or less would ensure that any side that gains sufficient advantage would be prone to launching a first strike. Because of this very fact the nuclear arms treaties between the USA and then the USSR limited fixed launch site while promoting mobile launcher and nuclear missile subs as much as possible as the guaranteed 2nd strike capability of both nations was what MAD was actually built upon.
But MAD is not without it's faults, heck so far i think Norway out all countries was the one that brought us closest to total nuclear war. https://en.wikipedia.org/wiki/Norwegian_rocket_incident
Yeah, right. And the Soviets most certainly took advantage of this moral error, for as you note, they're hard pressed to do so with a straight face otherwise.
There is no moral error here, only moral reality.
Also, it's not like our military establishment is separate from our civilian population centers. The SF bay area, New York, San Diego, among others, would be devastated in a counter-force first strike, no matter how precise.
The article says "a team of Norwegian and American scientists". I am not surprised.
The bigger issue is that they are more likely to initiate the strike if they know about this protocol and believe it will reduce the likelihood of a counter strike.
A while afterwards Reagan wrote that he long thought that the Soviet leadership, like the Americans, did not believe a US first strike was a serious possibility. But he eventually learned that this was a flawed assumption: The Soviet leadership saw the US as a possible - even likely - aggressor, and interpreted US actions accordingly. In that context, posturing was incredibly dangerous, and this realisation made him change tack and become determined to sit down and talk to them.