You are wrong with regards to Iran. If Iran obtains nuclear weapons they will use them against Israel. It is Iranian state policy to eradicate Israel.
The people of Iran live in a theocracy. The will of Allah, as interpreted by his Mullah's is paramount. They are not exposed to, or permitted to find out about the West's true intentions.
Israel, unlike Iran, has foresworn first use of such weapons unless:
1) Such weapons are used against them. That includes the threat to use them.
2) The survival of the state is threatened. i.e. The Israelie Army has been defeated and they are about to be overrun.
Which, as far as any Israelie is concerned, means a second holocaust.
Iran has not, and will not, give such an undertaking.