Why did MacArthur leave the Philippines?

The Japanese were pushing their attack on the Philippine Islands and the US Army was retreating towards the Batan Penisular. They were completely cut off. The only hope was for the US Navy to send ships to rescue them. However, the Navy was still suffering from the attack at Pearl Harbor. No forces were available to send. So MacArthur was ordered to leave. His capture would have been very demoralizing to the US war effort and the soldiers who served under him and in other areas of the Pacific theater.