I really think it is irrelevant whether Israel signed the Nuclear Nonproliferation Treaty or not. The point remains that it is dangerous for any mid east country to have them and the fact that Israel does, encourages other countries to strive for them as well. And, in spite of all the misinformation spouted about, Iran has never threatened to bomb other countries with nuclear weapons (it doesn't have them for starters), while Israel has indeed often threatened to bomb Iran, albeit not with nuclear weapons as yet. If there were a belligerent scale I couldn't say Iran would score higher than Israel.
UN: Gaza could be 'uninhabitable' by 2020 if trends continue (AP)
from the article: Turkey: World is turning a blind eye to Israel's nuclear weapons