I have no problem with native born Australians deciding to leave and take up residence and citizenship in another State, I do have problems with them then deliberately misusing their Australian passport in the service of their adopted State. Ben Zeigler didn't deserve to die in an Israeli prison but he chose to leave the land of his birth for Israel; to join the IDF and apparently Mossad and so to take his chances. Whether or not Zeigler could be fairly described as a traitor to Australia is unkown but the willing misuse of his Australian passport(s) is hardly loyalty to Australia. Its time to examine whether or not Australia should continueto accept duel citizenship, especially where a person enters another State's defence forces (either voluntarily or by draft). The pain that Zeigler's family is going through is real but not exceptional - pretty much similar to the pain felt by Palestinian familiies when they lose a family member by actions of Israelis. And unlike the Zeigler family, this they cannot avoid - they are pretty much locked into their areas where their movements are controlled by Israelis.
U.S. to defend Syrian rebels with airpower, including from Assad (Reuters)
from the article: The Prisoner X affair is a classic story of Israeli failure