I cannot understand how countries that possess nuclear weapons can, without even a hint of shame or guilt, tell other countries that they should desist from any effort to acquire them. Their argument is that only the nuclear haves are responsible enough to shoulder this burden. This is patent hypocrisy at best, and racism at worst. If they are so concerned about the dangers of these weapons, why don't they come up with a treaty to abolish all their arsenals in a specified time frame? Trouble is, none of these countries would voluntarily give up the 'big stick' (how big a clout would America (and previously the USSR) have had with the rest of the world had they not been in possession of a huge stockpile of atom bombs?).
To counter the argument that there is a danger of nuclear weapons falling into the hands of terrorists, I would say that there are two categories of countries involved here: (a) responsible countries who are mainly concerned with their national security (b) 'rogue states' who may be in league with terrorist organisations. Countries that belong to category (b) should be tackled by the United Nations in concert with the IAEA (and not by pre-emptive action by America). The fact that the weapons inspections worked very effectively in Iraq supports this approach. Countries in category (a) -- India is a good example -- should not have anything to fear.
Bottom line: Iran can have nuclear weapons, as long as it doesn't give any of them to Hizbollah.