its becuase Iran has lots of bad peoeple, if they had nukes then the usa would be destroyed
Well... that's a very simplified and over-doomsayer version.
The truth is that Iran is an Islamic Theocracy, which means that they use their holy book, the Torah, as their law book. When interpreted by the Iranian people, you get a culture that goes against everything Western Nations have built themselves on. This makes them very mad with Western Nations, which coincidentally, happen to be the most populated, most powerful, and most free nations on Earth.
I'm going to level with you. There was the Opium thing, Slavery, Imperialism, two World Wars, and a handful of Crusades. The West doesn't exactly have the best name for itself, yes, when looking at it from the Iranian point of view. However, one must remember what the West has done, advanced medicine to such a state where we can just change a bit of material about and it's a heart we can put in someone.
A beating heart. Roads, jobs, general advancement of Humanity, and, *ahem*, Universal Suffrage?
Onto the actual question, why can't Iran have nukes? Now, they can't. They're simply too unstable a country with a leader who's head would be better purposed as a form of alarm clock. Note how I said "Now". Any country can have nuclear weapons, be on the same playing field as any of the World Powers, but the big World Powers now, the USA, UK, France, Germany, China, and Japan, don't want too many nukes floating about that could ruin the general peace the world has seen for nigh over a century.
I mean, think about it. Thanks to Western motions like the UN, no major nation has declared war on another major nation since World War 2. And that's saying something, considering if you look back a few years before, when every other week somebody was trying to invade somebody.
And Iran would try to kill innocent civilians, just because the West simply doesn't fly the way Iran flies.
-Chillz