There is an entire Jewish ideology that claims that the 'Israel' cannot be created untill the Messiah returns, this would be a pretty decent attack on the Israel is a Jewish state dogma. Remember, atheist leftists are by far not the only ones anti-Israel.
http://www.youtube.com/watch?v=kh2mdPbYnZI
http://www.youtube.com/watch?v=GxiwBpbGmoU
Search for the documentary on Norman Finkelstein, he's a critic of Israel. Also search for his debates.
Focus on the economic aspects of the conflict. The more the economic reality is shown, the easier it is to dismiss religious claims.
Make sure to immediately step in if somebody calls anti-Israeli politics anti-semitism. My main two reasons:
http://en.wikipedia.org/wiki/Semitic
Palestians are actually Semitic calling Semites anti-Semitic doesn't make any sense.
If any criticism of a state is called anti-the biggest race in that state, how is criticism on any state possible? Is criticism on Nazi-Germany anti-white? Is criticism on China anti-Asian?
Also talk about the human rights abuses (you'll find plenty):
http://www.youtube.com/watch?v=Dm8v2C43_3A




