WASHINGTON — Barack Obama’s 949-word response on Monday to a question about foreign policy weakness showed the president at his worst: defensive, irritable, contradictory and at times detached from reality. It began with a complaint about negative coverage on Fox News, when, in fact, it was The New York Times front page that featured Obama’s foreign policy failures, most recently the inability to conclude a trade agreement with Japan and the collapse of Secretary of State John Kerry’s Middle East negotiations. Add to this the collapse of not one but two Geneva conferences on Syria, American helplessness in the face of Russian aggression against Ukraine and the Saudi king’s humiliating dismissal of Obama within two hours of talks — no dinner — after Obama made a special 2,300-mile diversion from Europe to see him, and you have an impressive litany of serial embarrassments.