Bragging about civilian deaths?

One of the questions we have discussed in class regarding war is when we're at war, are we fighting the civilians as well as the enemy's army? And is the murdering of civilians ever justified? And most Americans would agree that the civilians should very rarely be targets of our attacks.
Iraqis and Americans alike were appalled to hear of the atrocities committed by ex-soldier Steven Green, who is now one of six men on trial for the rape and murder of a 14-year-old Iraqi girl, and the murder of her family, including her mother, father, and 6-year-old sister. According to the article I found detailing the crime, Green and five other soldiers drank whisky, played cards and plotted the attack, and Green was reportedly proud of his actions afterwards, celebrating at a barbeque and saying "that was awesome" and "I did that. I killed them."
Obviously this crime shows that these men had incredibly low morale, and these men deserve to be punished for this brutal crime. But while the line between civilians such as this family that was murdered and our real enemies may seem very obvious to us, after spending time at war, the line became blurred for Green. According to Patrick Bouldin, a public defender, Green had sought help dealing with grief and stress after the deaths of close colleagues, and refers to Green's mental state before the crime as "a perfect storm of insanity." Bouldin claims Green was unsure whether Iraqis encountered were friend or foe, because "They couldn't tell the village people and the farmers from the insurgents and the terrorists." While it is hard for me to believe that Green mistook this family for terrorists, though it is hard to say because of his mental instability, this reminded me of Born On the Fourth of July, where Ron Kovic and his platoon accidentally murder villagers; women and children in a hut in which the soldiers believed hid the enemy. While Ron's was unintentional, both events convey the way civilians bare the brute of warfare when it's in their home country.
Events such as these make us consider the consequences of war. Civilians often are the ones suffering consequences of our soldiers' mistakes, and even if we take all measures necessary to prevent innocent civilians from losing their lives, accidents happen, and there is simply no way to guarantee that only our enemies are killed. Thus when we go to war, we are essentially saying that killing innocent people is a risk we are willing to take. They will always suffer the consequences of the violence we bring by participating in a war. Not to say we should always use nonviolent means to accomplish our goals, but we should be hesitant to go to war because not only will we lose some of our own men, but will unavoidably cause harm to innocents in the opposing country.
Green's actions were cruel and inhumane, to say the least. And while it is hard for me to put myself in his place, the crime is somewhat more comprehensible when considering how his best friends were killed by Iraqis; so, Green and some of his fellow soldiers, drunk and stressed and confused, went out and got them back. This gut-wrenching event shows us just how cruel war can be, how insane it can make soldiers, and how it causes horrific things to happen to innocent people. Tragedies like this are never justified, but because they inevitably come with war, can we ever say a war is one hundred percent justifiable? Is the loss of innocent lives ever justifiable?