President Obama should think before bowing to Saudi Arabia's new king in his Tuesday visit. King Salman has a history of funding al-Qaida, and his son has been accused of knowing in advance about the 9/11 attacks. When it comes to jihadism, Salman bin Abdulaziz al Saud is more of a hardliner than his older brother, King Abdullah, who died last week of a lung infection. As such, any commitment he makes to helping the U.S. destroy al-Qaida and Islamic State terrorists should be viewed with great suspicion. The 79-year-old Salman once ran a Saudi charity tied to al-Qaida and...