err, your "A propotionate attack in response to the Hamas incursion would surely be OK, but this is genocidal and so the ICJ has found the charges plausible," would seem to say that their response on Oct 8 was legal, probably the 9th...
But at what point was this line crossed. Your plea for a proportionate response would almost seem an invitation to a fixed number of civilian deaths. Myself, I'd say one dead civilian is one too many.