Obviously, since the comparaison comes from the function of the brain, we need to compare intra-species — not violence, but murder — among mamalians only.
And Grossman was not talking about war machines, but about individual massacres, and about the reluctance of individual riflemen to aim to kill.
So what’s your point about the 19th century or the 100 years war?
Let us go back to 1630s... When there wasn't much in the way of firearms (and the ones there were, were crap), and a lot of the hacking and slashing and murdering and raping and slave taking... yes slave taking, was happening up close and personal with pikes, and knives and clubs and swords.
There wasn't any problem with murder in large, industrial size batches there.
Remember the life expectancy in the 1630s. Those were not gray haired old men doing the killing.
Small group of thugs decend on a town in Thuringia, and kill the men, rape the women, and take whoever can stand a road trip, after killing the rest, up close and personal.
Rinse and repeat.
For all the loot those bastards took, they never got a single video game.
Your theory to ban video games is bad science.