Admittedly, MacArthur had an axe to grind, but he was also had knowledge of the enemy and their history of fighting to the last man. The arming/training of every man, woman and child for a homeland defense force is well documented.
Among the prime considerations Truman faced, was telling the American people that their husbands and sons, having survived years of war in Europe, wouldn't be coming home because they were headed for Japan. Bad mojo.
All things considered, we might have been better off letting the Russians take Japan.