The two presidents stood in the East Room on Tuesday afternoon, united in their goal of defeating the Islamic State but separated by a stylistic gulf as vast as the Atlantic. On the left, facing the cameras, was François Hollande, war president. He spoke of “cowardly murderers†who “dishonor humanity,†of a “relentless determination to fight terrorism everywhere and anywhere,†of “an implacable joint response,†of “hunting down their leaders†and “taking back the land.†On the right stood Barack Obama, President Oh-bummer. Defeating the Islamic State? “That’s going to be a process that involves hard, methodical work. It’s not...