North Korea, Iran and western arrogance.

The western alliance has nuclear weapons and it does not want unfriendly countries to have them as well. This is understandable. But is it wise to start imposing sanctions on those countries? The upshot of such sanctions would almost always be defiance, for no country could allow itself to be humiliated by outside powers who themselves have such weapons of mass destruction.
Just imagine how different the reaction from Iran and North Korea would have been if they had been treated with respect and friendliness and their concerns were addressed peacefully. The chances are they would have ended up being allies instead of enemies.