In the case of Lt. William Calley, President Nixon stepped in and pardoned him after he had spent three years under house arrest. Why Nixon did this is unknown, but it is beyond belief that he would do such a thing. For the end result is a slap in the face to every Vietnam Veteran who did their job and served with honor by adhering to the Rules of Land Warfare of the 1949 Geneva Convention which set the rules of engagement and expressly forbid the type of behavior exhibited by Calley and the thugs he commanded. They were not soldiers. They were thugs.
But while these egregious crimes have been trotted out at every opportunity by the anti-war movement, very little attention was paid to the horrendous atrocities committed by the North Vietnamese Army and the Viet Cong on their own people. One of the end results of the 1968 Tet offensive was the deliberate roundup and murder of as many as 5,000 South Vietnamese civilians--doctors, teachers, lawyers, businessmen--by the NVA/VC during the periods that they held territory. The most widespread atrocities occurred in the Imperial city of Hue. There alone the Communists killed over 3,000 South Vietnamese. This behavior was not widely reported by the press, and either ignored by the anti-war movement at best, or justified by them as necessary in a socialist revolution.
Additionally, not much of a fuss has been made over the intentional murder of American civilians (including missionaries and USAID workers) captured and murdered by the North Vietnamese. U.S. POWs did not fair any better. Those that were not murdered were systematically tortured by the North Vietnamese. Although these atrocities qualify as war crimes under the Geneva Convention, the lunatic fringe of the radical left condones those acts as "justifiable".