It's not a problem if a nation has nuclear weapons as long as it can absolutely keep them from being used outside its control. Nations should adopt the policy that IF they are attacked by a nuclear device, then they have the right to totally annihilate the nation who produced the nuclear material or weapon, no excuses. What is feared is the transfer of nuclear weapons or materials (for a dirty bomb) to non-state actors. States well know the consequences of attacking someone else with a nuclear device. Non-state actors, on the other hand, are not deterred by the same fear of retaliation or they have no place they care about protecting. Some state intelligence services may think they are clever enough to transfer nuclear materials to terrorist groups without leaving any of their own fingerprints behind. The more states that have nuclear weapons, the more possibility there is that someone will do something very, very unwise.
People aquire Atomic bombs to use them one day. it is not for show behind a glass room. if you have it, you will use it if you see the need. as long as there is double policies regarding these weapons by the powerful nations, there will always be a race among the countries to try to overtake each other in this technology, god save us all, if it is not controlled, the future of this planet will be a very messy and sh!tyy one. by barring one nation and allowing the other to have nukes will only create more mistrust and take this world to an unknonw future.