The ICJ is going to be examining what “Israel” did after October 7th…specifically whether “Israel’s actions constitute genocide.
You seem to have the impression that the charges brought to the ICJ are an opportunity for “Israel” to justify its actions, That is not what is happening. The ICJ is simply comparing “Israel’s” actions to the legal definition of genocide to see if they match. If they do, then “Israel” will be found guilty. It is irrelevant whether “Israel” had an excuse…genocide is a prohibited act for all UN member states…regardless of what the excuse is.