I really hope it's not "soft" to prefer not to destroy the entire planet :)
WW2 and the atom bombs are an entirely different debate, from a very different time. Nuclear weapons are much more powerful than the atom bombs that were dropped at the end of WW2, and they're also available to both sides in any likely future conflict.
The debate about pressing the button is always about mutually assured destruction. There isn't a way in which you win a war against another nuclear power. By pressing the button, you just make sure everyone loses much more quickly.
And I stand by the comment, we're in a bizarre world, where we have to say we'd press the button supposedly to stop the other side - and I do understand that argument, and maybe it's true. However, if Russia, for example, had launched a full strike against Europe and the US, life is over for us. Anyone actually going ahead and pressing in retaliation, is simply murdering millions of innocent people for the sake of an absolutely pointless revenge. The leader who presses the button would be committing atrocities many, many times worse than anything the Nazis did.