We all know nukes are devastatingly destructive and we hope to never be in the position to ever see it used, but as that man just said "it's better to have and not need than need and not have". No-one is asking if Corbyn is a warmonger or death hungry, it's the premise of, if it came down to it, would he use the deterrant if it became clear that such a weapon would be used against us, and his method is "Diplomacy", well in that sense i'll just leave this quote;
"Diplomacy is the art of saying 'nice doggy' whilst you search for a rock''