We would've been smart to listen if someone had. Our response to 9/11 is one of the most self-destructive series of actions any nation has ever undertaken.
Hamas should be annihilated, but I think there's a real question if the type of campaign Israel is waging right now is capable of doing that. Hamas may very well emerge from this strengthened in the long-term. Hell, look at the Taliban in Afghanistan. I don't know that there is a military solution to a group like Hamas (at least, I don't know that there is one that doesn't look like complete genocide). I think a political solution is more likely, and would certainly be preferable in that it would require less innocent bloodshed. But a political solution would require Likud to lose power, because they're pretty much full on fascist right now and fascists don't go in for political resolutions to problems. As long as Likud is running things in Israel, they're going to empower Hamas or someone like them.
But if moderates could take power in Israel and begin working with more moderate Palestinian groups? If they could get other Arab states to buy in to investing in developments in the Palestinian territories? Something like that could help minimize Hamas' influence and control, and ideally the Palestinians would eventually be able to deal with them themselves (it was, after all, primarily Iraqis that eliminated ISIS). There are a lot of people on both sides who want a peaceful resolution and the only reason a peaceful resolution isn't possible is because they lack the necessary political power, because Likud and Hamas are very fucking good at helping each other maintain their political control.
Obviously this would take a long time and doesn't answer what Israel should do today, but as a moral matter I think it should guide how Israel responds today. I said it yesterday, but if the Irish and the English could make peace, it's possible here too.