The trouble is, the Iranian leadership is not Pakistani, nor Indian, nor like any other nuclear regime. If Iran has nuclear weapons, one can be assured that some terrorist organization will also get access to them. What if Hamas had an Iranian-made nuclear device?
The Soviet Union once sought to intimidate, undermine, influence, subvert, exploit, deceive, penetrate, and dominate every country it had dealings with -- friendly or otherwise. It was paranoid and paralyzed by its dependence on the secret police. But today, the best course of action with Russia is to leave the damn country alone.