He described Japans attack on Pearl Harbor to a "T" back in 1925. He walked the plank for doing so.
The vast majority of those serving in the military and WW ll vets sided with MacArthur not Truman.
I could list more than a few dozen company and field grade and flag officers who went public complaining about how the war in Vietnam was being mismanaged/micromanaged and fought.
There are some exceptions, you ever hear of Carlson Raiders of the Marines Raiders of WW ll ? In the late 1940's Brig. Gen. Carlson resigned his commission as a Brig. Gen. so he could testify before Congress to save the Marine Corps and tell Congress that President Truman was one big ****ing ass hole big time.
Truman would confirm it when he fired Gen. MacArthur.