Letter of Last Resort

Check out this odd article in Slate about the "Letter of Last Resort", a doomsday verdict from the British prime minister instructing his country's nuclear subs, in the event of a nuclear apocalypse devastating Britain, to either annihilate back or just sort of let it slide. The rationale for the latter would be that killing tens of millions more civilians - i.e. the guys on the other side - might be the beyond-the-pale kind of mass murder (as opposed to more garden variety sorts of wartime mass murder).

The money quote is from Denis Healey, former defense secretary to Labor PM Harold Wilson, who'd choose "letting it go":

"I would find it very, very difficult indeed to agree to use a nuclear weapon—and I think most people would."

That's admirable. To many people, it might sound like crazy talk; and, for reasons well-articulated by the article's writer, a dangerous attitude to put out there regardless of actual policy. But can someone walk back Mr. Healey through less horrific weapons which cause slightly lower kill tallies, and determine at which point civilian death tallies become acceptable in revenge attacks? 

I mean, if you're going to take an ethical stand, that's fantastic. But once you do - once you concede that death is worth avoiding on the basis of its sheer moral repugnance - doesn't the floor drop out from under any hawk-ish stance at all? An alarming prospect indeed for those who don't take deadly carnage lightly.