You may be missing a legal wrinkle: the crime of incitement usually does not require the underlying primary crime to actually occur. (Admittedly I'm not sure if that is the definition in Israel, but they inherited a lot of British law so it is likely). So this does not require the Israeli population to accept that this was a genocide, only that some war crimes occurred and that they should be prosecuted. Right now they are not there, but the point is that the government has an incentive to keep the population in that state.