An interesting question in general, not just for children: Is it desirable at all to see videos of graphic violence, even if they are accurate? Does this improve anyone's judgement?
Gratuitously watching people die, I suspect, won’t really change anyone’s vote, or to volunteer, or donate. At least long term, because the violence usually is the attraction, not the conflict. And there will always be a new conflict.
A few key events in history have happened because of, lets say, acute exposure. But chronic exposure, to your point, possibly makes our judgement worse.
War is a neat little 3 letter word. The brutality that war inflict should be mandatory viewing so that we know what engaging them costs regular people.
Everyone should learn how the sausage is made. It makes it far more difficult to brainwash you with jingoism later on.