Iran's Genocidal Intentions

One of the central lessons to be drawn from the Holocaust is that when people proclaim that they're planning on killing us, it's a good idea to take them at their word. The Nazis were quite clear about their intentions, and they carried out those intentions as quickly and efficiently as possible. And they started on their genocidal rampage hoping to acquire better weaponery and technology in the process. By contrast, the Iranians are working towards the realization of those weapons before they launch their grand attack. Equipped with nuclear weapons, they could in fact commit 'instant genocide' if successful.
Words and intentions matter, and with the stakes this high, shouldn't the world understand that inaction amounts to the commission of sin by default.
The Convention on the Prevention and Punishment of the Crime of Genocide makes Ahmadinejad's pronouncements criminal and subject to prosecution. So why is he instead welcomed at the United Nations and other august institutions?