Alan Dershowitz has written a blog post on the Huffington Post that argues that what the Israelis did in stealing land is justified because one Amin al Husayni supported Adolf Hitler. Dershowitz is saying that even though the Palestinian people didn't exterminate any Jews in any death camps, Israel is still justified. Dershowitz is saying that Ahmadinejad lies when he says the Palestinians (collectively) didn't carry out the WWII war crimes.
All of this is irrelevant to the question of whether or not Israeli behavior is legitimate. It is not.
Alan Dershowitz is a distortion artist. He runs from the implications of truth. He hides behind half-truths at best. He is not for righteousness. He fights against it with all he can bring to that evil task. He is antichrist.