The facts remain what they are.
Gallagher stabbed a wounded, out of combat prisoner. The prisoner died. Those facts are not even disputed. Gallagher even bragged about stabbing him. The medic who confessed to killing him, after receiving immunity, said he killed him as an act of mercy AFTER Gallagher stabbed him.
Whether the prosecution made procedural errors or engaged in misconduct doesn't change the basic facts. Gallagher stabbed a wounded, out of combat prisoner. There have been posters here on this very forum who have cheered him for that, which I actually find kind of disturbing. The laws of land warfare exist for a reason. Gallagher violated those laws. He disgraced his uniform and brought shame on an old and proud branch of service.
He should have been tried in country and hanged in front of the civilian populace as an example to show everyone that we will not condone US forces committing atrocities.
Gallagher committed murder.