if Iran were to develop nuclear weapons there existence would be for deterrence value, to prevent the US from overthrowing the regime than for wiping Israel off the map, which would be suicidal.

the other point I wanted to make above is that India and Pakistan very nearly had a nuclear exchange a couple of years ago after a couple terror attacks in India (in the legislature and an army base where 22 soldiers wives and children were murdered). All of this was intended to goad India to attack, so when it mobilized the Pakistanis threatened to use nuclear weapons. Both sides backed down - and in this case the presence of nuclear weapons (in hindsight) probably prevented a war.

I tend to agree with Gwynne Dyer on this one
nuclear Iran?
Petr