Ironically, the prisoner shared Sot's outlook. The people he killed, in his mind, were "bad people", and so no trial was necessary.
Loan and Sot agree. The difference is, Loan was in the middle of the Tet offensive, with the enemy everywhere, killing not just soldiers, but innocent women and children. Which was Adams' point. We need to consider the circumstances, which are extenuating for Loan.
Sot has no such excuse, of course. Nor did the Viet Cong fighter, who rationally planned the attack.
Sot excuses:
He would be a prisoner detained with his hands tied behind his back if he was executed after a trial.
I think most of us would consider a trial to be required before an execution.