An Israeli friend (who lost his son in a PLO attack) puts it like this.
What would happen if Israel puts down all its weapons? No Israel.
What would happen if the Arabs and Iranians put down all their weapons? Peace.
The Palestinians and Israelis used to live in harmony together, until the PLO raised the stakes on homeland etc. - an insoluble problem. Everyone says they have the right to be there, we were there first, God gave it to us etc. etc.
Israel NEED to keep their (officially undeclared) nuclear arsenal to keep the peace. They have only ever threatened to use it to prevent their neighbours from acquiring the means to carry out their publicly declared and oft repeated determination to wipe Israel off the face of the earth.