AND the country.
One assumes MacArthur having fought under FDR for 12 years felt Truman was a pretender, and not capable of grasping the military ramifications in the Chinese/Korean arena. MacArthur wound up correct (unfortunately for the 50,000 Americans who died in Korea.)
Both Truman and Nixon were the Rodney Dangerfields of U.S. Presidents.
Oh, MacArthur thought he knew more about pretty much everything, than pretty much everybody. He just ran hard into that pesky "chain of command" thing, and discovered to his amazement he was not actually at the top of it. ;-D