The MAD doctrine depended on both parties being rational and understanding the consequences of a nuclear war where there would be no winners. At least twice during the Cold War, Russian commanders avoided launching nuclear missiles despite pressure to do so. The Iranian mullahs do not have a rational world view and believe that the destruction of the US and Israel is a religious duty and the resulting global cataclysm would fulfill their prophecies. With nuclear weapons they would pose a greater threat an apocalyptic global war than even the unhinged North Koreans.
“ With nuclear weapons they would pose a greater threat an apocalyptic global war than even the unhinged North Koreans.”
An exchange between the USA and USSR involving 10,000 weapons on each side would have been apocalyptic.
Iran committing suicide by delivering a gunbarrel Hiroshima bomb in a US harbor would not be apocalyptic.
Speaking about Iran “destroying America” is just histrionic propaganda.