Surely the problem is not that Iran would start launching nuclear bombs on israel (they aren't that stupid). The problem is that they could indirectly attack jewish and israeli targets around the world with virtual impunity. This would also start a nuclear arms race in the mid east. Saudi Arabia and Bahrain aren't going to be able to live with a nuclear Iran.
U.S. confirms ISIS computer expert killed in air strike (Reuters)
from the article: Can Israel live with the Iranian bomb?