Do you think there is ever a use for nuclear weapons in a peaceful world? And is it ever justifiable to use WMDs (weapons of mass destruction) in warfare?
I don't think there is a use for them in a peaceful world- the mutually assured destruction theory (if everyone had nukes, no-one would use them, 'cos if they did, they'd get nuked back) relies on everyone being sane. Take one crackpot, to fire one nuke, and everyone on the planet dies.
As for justifying their use in warfare... you kill so many people, and affect so many lives for generations to come. Can you really say it was worth protecting your own people (even though they could be harmed too) to harm so much innocent life? And, yes, nukes will always harm innocent life when used in warfare.