Some might see Vanunu as a hero but legally he is a traitor he has also made more problems for everybody through his actions. Before Vanunu there was the nuclear ambiguity policy ( the arabs knew about the nukes but said nothing because there was no admittance to anything ). When Vanunu went public it made Israel's nuclear program more public and made ambiguity a harder policy to operate. Love or hate Vanunu he is a traitor and 99% of the Israeli public recognise him as such. He also didn't do what he did out of some sense of morality it was because he was a low level technician who had been passed over for promotion and he was bitter and wanted his revenge. Its his supporter who consider him a hero and its an image he has been happy to embrace, better to be a hero doing it for morality than a bitter technician wanting to get his own back at the system that didn't appreciate him.
Netanyahu condemns West Bank arson attack, calling it 'terror' (Haaretz)
from the article: Snowden’s America, Vanunu’s Israel