It's war. War has unfortunate and unavoidable casualties. Israel didn't choose this war and has done everything it can to avoid it. Including pulling out unilaterally from the entire Gaza Strip in 2005.
The Palestinians were left to govern themselves and elected Hamas. Hamas has received hundreds of millions of dollars in aid from all over the world, including Israel. Israel supplied water, electricity, gas, fuel and work permits in Israel. Yet, instead of Hamas choosing to build civilian infrastructure and help the Palestinians, the leaders embezzled millions and the cose to build rockets and terrorism infrastructure and pay terrorist salaries.
Israel stood by and watched the world turn a blind eye, again and again, to rockets being fired i to civilian populations. Name one country that would allow that to happen to them and wouldn't retaliate. We're done with the so-called "proportionate responses". What is the proportionate response to decapitated babies? To butchered toddlers? To kidnap and rape, and abduction of the elderly?
There is no peace to be made with an organization that lives up to it's charter claiming its intentions to kill you.
Israel and the Jewish people swore that the holocaust would never happen again.