Who is "they"? What role do the civilians being killed play in the decisions of their state?
It used to be only muderous tyrants easily found convenient excuses to wantonly kill civilians. I am glad we are so much more advanced now.
This is a common philosophy now because we know as even with the most advanced military in the world we are vulnerable to attacks on civilians, and because in foriegn policy we use it to sell the public on a regime we do not like being evil.
However civilians have always been legitimate targets in warfare. Thier taxes are what funds the military, thier economy is what keeps the military functioning. In a democracy even more so than anywhere else because they as civilians choose who is in charge. Iran is a democracy. Civilian factories and workers are the makers of bombs, the creators of technology in the weapons, the creators of the weapons and vehicles themselves. We understood this in WW2 when we carpet bombed cities and factories filled with civilians. We understood this when we nuked one city, saw the civilian death toll, and proceeded to nuke another city. Also consider most countries have mandatory military service, and that in time of war all the soldiers killed on the battlefield
will be replaced from willing or unwilling recruits from the population of civilians. In America for example all able bodied men are part of the informal militia (per the Constitution) from which soldiers may be drawn from. If not enough soldiers are available voluntarily and there is need, they will be drafted, period. This is the case around the world. The military cannot and does not fund themselves, they only can function with the taxes and economy and goods provided by the civilian market.
We are all in it together, trying to raise the white flag because you are a "civilian" when our very constitution says we are all part of the militia is ironic at best. As long as thier is a civilian population to draw from, thier
will be replacements for every single soldier that dies on a battlefield. Civilians are not indifferent or seperate from the decisions of thier leaders if they choose who thier leaders are. Whether they choose by voting for them in a democracy, or whether they choose by not revolting and overthrowing them in another form of government, they are the ones ultimately responsible for what is allowed to be done by and in thier nation. They always outnumber and must fund and support those in power for them to function.