I cannot imagine a single person who believes that the destruction of nuclear weapons and the potential threat that they pose is not serious and devestating. As one scientist put it, now man has finally figured out how to destroy humanity. However, in the field of international security and international studies, nuclear weapons are analyzed as means of measuring political power, political will, and level of threat which dictates relations between countries. Nucluear proliferation is perhaps the main security concern of every country, especially those "major or regional" powers. The arguement that follows is that those who have the weapons are more apt to use them, escalating the level of violence in wars.
However, proporters of Realism (where all state interactions are based on a balance of power theory, where those with the most military might are always on the most powerful international players and can forgo international institutions) will argue that nuclear proliferation actually stabilizes regions and relations between countries because it balances the level of military power. Take for instance the United States and Russia during the Cold War. While tensions and military aggression rose on both sides, neither side was willing to risk full on war with the other because of the threat of nuclear retaliation and total destruction. Another example, is the recent emergance of a nuclear India and a nuclear Pakistan. Since both countries have aquired nuclear capabilities, the amount of violence between the two, especially over the region of Kashmir, has decreased significantly. It appears that nuclear profleration has its benefits and prevents confrontations between major powers.
This brings us to Iran and the United States. Iran is seeking nuclear capabilities while the US and the international community are pushing for it to cease its activities. Based on the experiences of the Cold War and the more modern example of Pakistan, is a nuclear Iran really a bad thing? For Iran to attempt a nuclear attack against the US or other power would be state suicide, and they would be immediately destroyed by a counter attack. A nuclear Iran would also balance it against its strong Middle Eastern neighbors, leading to perhaps more stability in the region? Debatable but a thought.
There are no right answers to this question. While I am typically aligned with the view that no nuclear weapons would be better for humanity, I cannot ignore that they exist and will never go away. As such, it is important to look at their strengths and weaknesses as means of negotiation in the international arena and analyse them from there.