The military goals aren't very clear. "Ending Hamas" is vague. It's not all that clear where Israel wants to end up after the war is over. What's supposed to happen to Gaza?
Also, what are the rules of engagement, and can they be justified? (A bare assertion that IDF tactics are justified is not enough to satisfy my curiosity about what's going on.)
Explaining all that would be more in-depth than I'd expect anyone to write in an Internet comment - it would take a longer article. But these are the things I'd expect if Israel were serious about justifying its actions to an open-minded but skeptical audience, and I haven't really seen it. Perhaps I've missed it, though?
(Although I don't think the invasion of Iraq was justifiable, it's notable that the Bush administration tried to justify it. For example, famously sending Colin Powell to the UN to make a speech about weapons of mass destruction that turned out not to be true. I also remember reading about serious planning for occupation after the war. That didn't go like they expected.)