In WWII, in fact in every national contest for survival (that's what wars are, you know) up until the beginning of PC war, Korea and Vietnam, we understood that the people who assisted the enemy in any way were legitimate targets.
The man who worked in the machine shop that produced telephones for the German government was a target. The woman who helped harvest rice that fed the man who drove the bus that took the troop moving trolley car operator in Tokyo to work was a target. If you lived in Fascist Italy, you were a target.
War is horrible. Imagine your worst war nightmare and multiply it 100 times over. It is worse than that.
But then realize that any and every thing you do to make war less evil only prolongs the killing, and that killings kills Americans, Brits, Afghanis, everyone.
It's horrible, but it is reality.
War is the ultimate Armageddon-like reality, but it is the only way to win that war.
If that's the case, does that apply to us too? According to you, are our civilians supposed to be legitimate targets? If not, what is the logical difference between our civilians and theirs?