Delegations from 32 countries walked out as Iran President Mahmoud Ahmadinejad was addressing the opening session of the United Nations General Assembly a year ago. “It is unacceptable,” declared then-UN Secretary-General Ban Ki-moon, referring to Ahmadinejad’s speech, for the General Assembly “platform ... to be misused in this way.”His assessment was spot-on, and the delegations that walked out – representing all 27 European Union nations, the United States, Australia, New Zealand, Canada and Costa Rica – delivered an important message: A radical Islamist regime that acquires nuclear weapons will drastically alter the world order and pose a genuine threat to Europe, the Gulf and other Middle Eastern states and Israel.All delegations committed to peace and human rights should walk out again during the Iranian leader’s speech on September 22, proclaiming, “We’ve had enough.” Better yet, they should not even show up for the speech, and explain why.Since last year’s opening session, Iran has accelerated its drive to acquire nuclear weapons and continued to thumb its nose at the UN – the very same body it is addressing amid pomp and circumstance – and at the UN’s International Atomic Energy Agency (IAEA). Iran’s actions have been so egregious that UN Security Council members last week denounced Tehran’s failure to abide by four sets of UN resolutions to cease enriching uranium.Germany’s ambassador to the UN, Peter Wittig, said his government was concerned by Iran’s intention to arm missiles with a nuclear device. US ambassador Susan Rice said Tehran’s installation of a uranium-enrichment facility and heavy-water reactor near the city of Qom constituted a violation of UN resolutions and a “clear provocation.”Iran, in fact, has refused to answer IAEA questions about these “activities of a possible military dimension” since 2008.Developments this summer make Iran’s nuclear program cause for even greater concern and provide additional reasons for walking out on Ahmadinejad’s UN speech. These developments include: Iran’s announcement that it will enrich uranium up to 20 percent, close to weapons-grade and beyond any justifiable civilian need; its secret tests of missiles capable of delivering a nuclear payload; Iran's Revolutionary Guards’ firing 14 missiles in an exercise, one of them a medium-range weapon capable of striking US targets in the Gulf or Israel, and Tehran’s announcement that it is moving centrifuges to an underground bunker.The threat of a nuclear arms race in the region is a clear and present danger should this behavior continue unabated, and there is little reason to think such an arms race will stop at the borders of the Middle East. At this time of upheaval and change should the world be complacent with regard to nuclear weapons in hands of unstable and nascent governments? Furthermore, Iran is exploiting the turmoil of the “Arab Spring” and the attention the pro-democracy movements are getting in order to advance Tehran’s fundamentalist Islamist ideology, expand its regional influence and exacerbate tensions. Iran’s rulers seek to destabilize the region and prevent what these movements aspire to – democracy, freedom and peace in the region.The rulers’ actions also aim at deflecting attention from their repression of their own people.The most contemptible example is Iran’s assisting Syria’s brutal suppression of peaceful, pro-democracy demonstrations that the UN says has killed more than 2,200 people since March, in order to preserve the government of Syrian President Bashar Assad, a close ally of Tehran. The EU last month charged that the Al-Quds forces, an elite unit of Iran’s Islamic Revolutionary Guards (IRG) provided “support to the Syrian security services to repress civilian protest movements.” For months, published reports have cited the presence of IRG and Al-Quds forces throughout Syria.At the same time Tehran continues arming, training and funding its proxies; Hezbollah in Lebanon via Syria and Hamas in Gaza. Earlier this summer Turkey informed a Security Council panel that on March 21 it seized a cache of weapons from an Iranian cargo plane.The plane was bound for Aleppo, Syria, and the weapons were listed as "auto spare parts" on the plane’s documents.On March 16 Israeli commandos boarded a ship bound for Gaza with 50 tons of Iranian weapons on board, including advanced anti-ship missiles.That same day Egyptian authorities announced that they had seized Iranian weapons on trucks going from Sudan to Gaza.The UN delegations can cite these and many other threats to world peace and stability, and many other human rights violations as reasons for walking out during the Iranian president’s speech at the UN, or for not showing up. Iran’s rulers have proven that they should not be considered a member of the family of nations – and should not be treated as such by the international community.The writer is the Executive Director of Global Affairs for The Israel Project.