Pat Condell hit another home run in the following video where he points out that Palestinians get a free pass for their behaviour because they are not held to the same standards as Israeli Jews:
Condell blames the collective attitude by the West as racism. The West doesn't expect Palestinians and other Arabs to behave like normal Western human beings would.
I agree with that this is a major element but I also agree with Why Evolution Is True that there is a "traditional sympathy of liberals for the perceived underdog."
I also believe that there is also a faction of anti-semites within the Far Left that overlook "inconvenient facts" when it comes to Israel.
If you don't agree with Condell, then why is Israel such a focus of hatred and criticism when a lot more deaths and murders or innocents have come out of Darfur and more recently Syria? It is because we collectively expect barbaric behaviour from Arabs and/or Muslims. And besides, there aren't many if any Jews involved in the Syria or Darfur conflicts either.