Oh, it’s absolutelly cultural, probably derived from empathy (check the Vulnerability chapter in the paper in my second link), and it seems to be almost universal at least in the modern Western World.
And indeed, going back to the very beginning of our discussion, I was giving emphasis to the killing of children by the Zionists as an especially abhorrent crime because I do share that feeling as I am part of that culture just like I expect are the majority of those that would read my post. I don’t write comments to convince the tiny subset of people who find it easy to have a very detached view on the purposeful killing of human beings, I write my comments to convince most people and I wasn’t even being manipulative because the take I have on the morality of child killing is based on the feelings I have on which deaths are more abhorrent which seems to be the same as most people likely to read my comments.
That said, a purely logical and as objective as possible analysis would still yield that the murder of children is generally a worse act than the murder of adults, simply because children have in average a lot more years as a productive citizens ahead of them than adults: in pure, emotion aside, almost Accounting terms, targetting children in a war is targetting the Future of a nation by taking out their Future productive capability.
In fact, I wouldn’t be at all surprised if that’s exactly the calculation that the Zionists made - if one has no empathy and hence no sense of added abhorrence when it comes to child murder and one has as a strategical objective to weaken now and forever an entire enemy ethnicity, it makes logical sense to target the children of the “enemy ethnicity” in order to further that strategical objective and the absence of empathy guarantees there are no pesky feelings like guilt getting in the way.