There's only one honorable response, and it couldn't be simpler: A complete and immediate arms and dual-use technology embargo of Israel, combined with more general sanctions. South Africa should be the model: Just ostracize them as much as possible. Say what you will about Russia, but Israel can
never be self-sufficient, and China (justifiably) appears to despise them, so sanctions and embargoes would be substantially more effective in correcting their behavior.
This will never happen, and we know why. It's disgusting. The "enlightened," "liberal" west's principles have never been more clearly on display: "Why should we concern ourselves with the wholesale slaughter of innocent children in a pent-up captive civilian population? Not our problem."