Military force is an occasional necessary evil. What if in WW2 the Allied forces had not stopped Hitler and the Axis powers? What were the Germans doing to Jews, Gypsies, Slavs, Bolsheviks, homosexuals, the mentally ill, developmentally disabled, the physically handicapped and other "undesirable" non-Aryans? They was slaughtering them by the millions.
As for the soldiers themselves, it is a matter of self-defense under battlefield conditions.