Here are the questions which should be asked about any military operation:
1) Is the strategic objective a good one?
2) Will the operation likely bring about the objective?
3) Does the objective justify the means used in the operation?
Israel has a good strategic objective -- to stop the arbitrary bombing of Israeli civilians by Hamas. More broadly, it aims to reduce the number of Israeli casualties as well as to reduce the terror caused by the rocket attacks. These are understandable and perfectly commendable goals.
But will the attacks on Gaza bring about that objective? I'm quite skeptical, and the recent failure in Lebanon only brings more skepticism. The truth is, it's just not that hard to fire missiles into Israel from right next door. Killing a bunch of Hamas policemen isn't going to stop it. Qassam rockets don't need uranium or centrifuges or radar or aircraft or special fuel or even a big launcher. Anybody can make one in his basement with a few common tools and components.
Not only will the attacks probably fail to bring about the objective, but there is a good chance that they will bring about the anti-objective. By killing so many Palestinians and terrorizing and inconveniencing and making the lives miserable of so many more, they mobilize anti-Israel and anti-semitic sentiments among the Palestinians. The inevitable reprisals will no doubt kill more Israelis than all the Qassam rockets in the history of the conflict. And that's not even counting Israeli soldiers who die during the operation.
The biggest problem with the operation, though, is the answer to the third question. Does the objective of stopping the rockets justify the means Israel is using, even if it did acheive that objective? I guess that depends on the ratio of Palestinian to Israeli casualties you deem acceptable. Is it acceptable to kill a hundred Palestinian civilians and destroy the homes and livelihoods of thousands of them and the infrastructure that supports millions of them to save a dozen Israeli lives?
I'll leave you with two paragraphs from Matthew Yglesias:
One way to reply to [the idea that intentions are what matter] is à la Ezra Klein who observes that at some point you need to judge based on what’s actually happening. And what’s been happening is that whatever Hamas’ ambitions may or may not have been, they were scattering short-range inaccurate rocket fire on Israel that was causing little damage. Israel struck back with actions that have killed hundreds of Palestinians and pushed over a million more closer to the brink of starvation. And in general this is an important aspect of the conflict — irrespective of intentions, over the years you have many more dead Palestinian civilians than Israeli civilians.
But another piece of the puzzle is that though American Jewish liberals tend to take a lot of comfort in the idea of Israel’s good intentions and good faith throughout this whole process, there’s a reason approximately no Arabs anywhere in the world see it that way. All throughout the “peace process” years — through the good ones and through the bad ones — Israel continued expanding both the geographical footprint of its settlements and the population living upon them. For most of this time, Israel has often appeared unwilling to enforce domestic Israeli law on the settler population, to say nothing of abiding by international law or agreements made. And while Israel has stated a desire to leave the Gaza Palestinians alone in their tiny, overcrowded, economically unviable enclave, the “disengagement” from Gaza has never entailed letting Palestinians control their borders or exercise meaningful sovereignty over the area. The proposal has basically been that if Palestinians cease violence against Israel, then the Gaza Strip will be treated like an Indian reservation. Israel’s policy objectives in the West Bank appear to be first seizing the choice bits of it, and then withdrawing behind a wall with the residual West Bank treating like post-”disengagement” Gaza.
You can argue until the cows come home about who has the moral high ground, but at the end of the day Israel has killed far more Palestinian civilians than vice versa, not only in this military action, but throughout the history of the conflict. Israel has continued to build "settlements," often aimed specifically at expanding Israel's territory and strategic holdings and to make a self-contained Palestinian state impossible. In doing so, it's not only been morally wrong, but breaking its own laws.
There is no excuse for Hamas to fire rockets at Israeli civilians. But just because Hamas is a terrorist organization doesn't mean that anything Israel does in response is justified. Israel must make sure its military operations are both effective and moral. The framing of the argument away from those relevant questions to a place where Israel gets to play the wholly innocent victim ("We aren't allowed to defend ourselves??" "We're worse than Hamas??") and much of the western world gets painted as antisemitic is just disingenuous.
Please don't respond by asking for alternatives, or by saying Israel has to do something, as if the lack of alternatives makes any counterproductive and immoral operation a good choice. And don't whine about media bias or antisemitism or any other change of topic. You have to demonstrate that this specific military action is moral and likely to succeed in order to win this argument.