The only thing that can stop a Bad Country with a nuclear weapon, is a Good Country with a nuclear weapon. That would be another way to phrase it.
You think the sanction and opprobrium of many nations is not adequate to discourage them?
Iran is no good country to have an A-bomb, If they have a dozen Saudi Arabia will feel the need for two dozen.
North Korea does not deserve the stability it has , and it has had this stability for fifty years without an a-bomb, with the A-bomb they deserve respect?
Does North Korea respect all of the countries that have more than a thousand a-bombs each?
They want respect so badly that they are spending away all hope of being respectable to get it , and they don't even realize that they do not respect the nations that are ahead of them on that path.
If sanctions are enough we may eventually embargo our way to a world with few nukes, if not we do need the good countries to keep ready with a nuclear reprisal.