^TBH, I wish I didn't answer that question. That was poorly thought out and hasty. The proper answer would be VERY difficult to type out and explain, and honestly very few people fully understand it. I strongly suggest you spend a lot of time researching that topic. It is extremely complex and not as clear cut left/right thing as it seems. You can argue for either side till you're blue in the face, and you'd be right either way.
The rough gist of it is that a lot of people perceive(and not without justification) the Palestinians to be oppressed by the Israelis. Seriously, life as a Palestinian isn't fun. The alphabet mafia, having long been victims of oppression, naturally empathise with the Palestinians. Which is all fine and dandy, except quite a lot of Palestinians are fairly devout Muslims for whom the alphabet mafia would be complete anathema to their way of life. Herein lies the paradox of the modern-day lefty.