Hamas is / was an Iranian proxy. Iran took illegitimate and terroristically motivated advantage of justified feelings of injustice of Palestinians. The situation they are born into by no fault of their own, is unfair, horrible and unjustified. Iran channeled this rage into pointless crimes against 🇮🇱
The reason why it's a war crime to use children in war, or to fight the war in civilian clothing (like how Hamas does it) because if you do that, the enemy will not look at uniformed soldiers as a threat, they look at people wearing civilian clothing and kids as a threat.
A warcrime on one side does *not* justify a warcrime in retaliation. Warcrimes are absolute and mustn't be committed period. Otherwise, we hollow out any international law.
So, if you use children for fight, the enemy troops will start seeing children as potential combatant. That leads to children getting killed. If a soldier thinks kids might stab them, they'll be much more likely to shoot children. That's why Hamas is doing it. They use children and blame the Jews.
I get the logic. Makes it complicated, but it doesn't make it right to kill or starve innocent children. That's not self defense.