The murder of U.S. Ambassador J. Christopher Stevens in Libya on Wednesday is the direct consequence of President Obama’s weakness as a leader. His administration’s support of Islamist uprisings across the Middle East have led to a destabilized region where radical anti-Americanism is running rampant. The images being transmitted across the planet today give a glimpse of what the world looks like absent strong U.S. leadership in international affairs: Rioting mobs ripping down the American flag from our embassy in Cairo and a diplomat’s brutalized body being dragged through the streets of Benghazi. These are not isolated incidents but the...