THE SLAUGHTER of eight young yeshiva students and the wounding of nine others by an Arab terrorist in Jerusalem last week was a cold-blooded act of evil. It is difficult to make sense of the depraved fanaticism of someone like Ala Abu Dhaim, who calmly entered the school's busy library, took three guns from a box, and sprayed the room with hundreds of bullets before finally being shot dead by an off-duty military officer and a student who heard the gunfire and came running. Even more perverse than Abu Dhaim's massacre, however, was the behavior that followed it. In Gaza,...