The answer is simple, they are being killed by other Arabs with no way to blame Israel so no one cares.
The Lebanese Army is attacking a Palestinian refugee camp with tanks and artillery. The New York Times reports:
The official death toll from the two-week conflict reached 110 including 44 soldiers. But the death toll of militants and civilians inside the camp is widely expected to grow much higher as bodies are sifted from the rubble.
Where is the UN condemnation? Where is the British government lecturing about disproportionate use of force? Where is the US State Department spokesman calling for restraint? Where is Saeb Erekat and his claims of a massacre?
Just think back to the world reaction when Israel entered Jenin 3 years ago. There is no better proof of the anti-semitism and double standard of the world then what is going on now in Lebanon and the world's non-reaction.