He could have actually explained this in a politically neutral way, devoid of contemporary issues that will be meaningless before the child even gets to middle school, telling the child that even in war, infliciting more pain or harm than is strictly necessary is wrong and against the law, and then explaining the principle of proportionality in terms a four-year-old would understand, and telling him mercy to the fallen solves more problems than simply taking revenge against them as a group.
But no, he had to **** over his grandkid's brain with garbage, which will make no sense at all when the poor little guy gets old enough to start understanding the larger context of society. What a shitstain. What a disgusting, brain-maggot-infested shitstain.