I tend to oversimplify, I suppose, but I see a difference. The issue isn't with Iran giving nukes to al-Qaida.
1) War by proxy. You are both correct and incorrect when you say Iran has only been in one war in the past few decades. In addition to their war with Iraq, they have fought a proxy war with Israel through Hamas and Lebanon. There has been a decrease in attacks since Syria has been in military control, sure, but the fact remains that Iran materially supports Hizbullah's rocket and terrorist attacks against Israel.
To me, the term "State sponsers of terrorism" says it all. Radical Islam, whether shiite or sunni, has shown itself capable of any act, even that of self destruction. The Middle East basically got a free ride after WW2, where Nazi-aligned supporters of genocide and hate were allowed to continue with a "clean slate". Egypt's Nasser, the "Palestinian Hero" the Grand Mufti, and many others were allowed to thrive. Saudi Arabia has sheltered many since, like Edi Amin, who praised Hitler as a Hero.
This, in my opinion is enough of a dark cloud over their society to create a situation where trust should be earned, not simply granted out of fairness.
2) Instability. Iran is an inherantly instable nation, only a few decades old, with numerous factions hoping for "change". That change could be peaceful Democracy, and that change could be toward the radical violence of the 1970's and 80's. If we do trust the current government enough to allow them weapons technologies, there's no way for us to know if their teetering power will last another 5 years.
The fall of the Soviet Union highlighted this, as small, desperately poor break-away republics were suddenly left with the weapons of superpowers, and little or no obligation as to what to do with them.
3)Our own sins are warnings. "Law Enforcement" is the most hypocritical act, and yet the most necessary. People always list the sins of the US and other nuclear nations when they talk about new nuclear powers. Sins are sins, though. If a policeman breaks the law, that doesn't give everyone the right to, or the moral obligation to his powers. The wrongs commited by the US and others shouldn't be used to validate the wrongs by other nations.
The whole "They are no worse than us" arguement relies on a lot of faith. Intent, the attitude toward the wrong in question, has much more to do with it. Sure, China has no more moral reason to have nukes than North Korea. Frankly, China shouldn't have them. They do, though, which creates untold problems when we try to deal with their human rights issues, and Taiwan, and all the rest.
I think you have to cut through the veil of "equitability", and subjectively judge. North Korea and Iran are basically hateful nations, who have used almost every opportunity since their beginning to thwart the will of the international community. North Korea is a nation which kidnapped Japanese citizens, test fires missiles by firing them over Japan. Iran has been an open proponent of the idea that Isreal should simply not exist, and materially supported any means to harrow and harm them by terrorist organizations.
Sure, it is hypocritical. Pakistan shouldn't have had nukes, but they do. China shouldn't have them, but they do. Maybe we shouldn't have them, but we do. DIS-arming a nation is next to impossible, but preventing them from becoming armed is pro-active.
It's not like the world is a better place with more nuclear weapons. There shouldn't be any. To say that because your neighbor has a closet full of WMDs gives you the moral right to have them falls flat. To say that because the police sometimes abuse their authority that you should also have the trappings of that authority, the weaponry to impose your OWN abuse, falls flat.
