It is now impossible for US politicians to ignore the slaughter in Gaza: more than 3,500 Palestinians have been killed in the 12-day barrage, including the 500 reportedly killed Tuesday at Al-Ahli Arabi Baptist hospital. Some 50 entire families have been wiped out — every living relative, including children and babies, gone. And Israel has issued a directive to those remaining that amounts to an ultimatum: leave northern Gaza, all 1.1 million of you, “for your own safety” — in other words, evacuate or risk death in the impending blitz and ground invasion. The United Nations says such a mass...