He notes that with the exception of the Cuban Missile Crisis, every justification for war since 12945 has been way overblown:
5) Threat inflation. As I think about this war and others the U.S. has contemplated or entered during my conscious life, I realize how strong is the recurrent pattern of threat inflation. Exactly once in the post-WW II era has the real threat been more ominous than officially portrayed. That was during the Cuban Missile Crisis in 1962, when the world really came within moments of nuclear destruction.
Otherwise: the “missile gap.” The Gulf of Tonkin. The overall scale of the Soviet menace. Iraq. In each case, the public soberly received official warnings about the imminent threat. In cold retrospect, those warnings were wrong — or contrived, or overblown, or misperceived. Official claims about the evils of these systems were many times justified. Claims about imminent threats were most of the times hyped.
He is talking about how Iran is the current Hitler of the week, and how the threat is almost certainly overblown.
As I would observe, even in the worst case, Iran is not going to give nukes to terrorists, for the same reason that the Soviets and the US never let nukes out of their direct control, and they are not going to launch a nuclear attack on Israel, Hezbollah does just fine in prosecuting their interests in that area, and Israel has a substantial nuclear arsenal (somewhere around the 6th largest nuclear power in the world) which would make an attack suicidal.
What a nuclear Iran would mean, however, is that the United States would be prevented from acting unilaterally against Iran, which is seen as a disaster for US military and foreign policy.