There are two basic strategies for fighting terrorism. One is employed by the United States, Israel, and Russia. The other by most of the rest of the world. Countries like India, Spain, France, and Italy use the method of containment--prosecuting terrorists as criminals and leaving it at that. The U.S., Israel, and Russia prefer making war on someone. Great Britain has used both approaches--the first with the IRA, the second with Al Qaida.
The containment approach has the advantage of limiting the damage. There's a terrorist attack, people are killed, some perpetrators are arrested, in a few months things return to normal for all but those directly affected. For them it's a continuing trauma, but no more so than for any plane crash, earthquake, fire, hurricane, train wreck, flood, or other calamity.
The make-war approach has the advantage of discharging the desire for revenge. Revenge is hard come by, of course, in cases like 9/11, since the perpetrators are already dead. And you can't make war on their leaders, because they're individuals, not a country, and they're hard to locate. And you can't make war on the country they and their leader came from--Saudi Arabia--because it's an ally. And you can't make war on the country their leaders are hiding in--Pakistan--because it's also an ally. So your only solution is to inflict terror on a third party, like Iraq, even though it had nothing to with 9/11. But this will only make you feel better for a little while, since after you've destroyed this country, you find you've created thousands more terrorists than you started out with, and now you have to find someone else to make war on, since you've already made life as miserable for the new terrorists as you possibly can.
(Finding a country to make war on was even harder in the case of the Oklahoma City bombing. Since Timothy McVeigh was 'harbored' by the United States, we would have had to make war on ourselves, and hence were forced to employ the containment approach.)
It's more satisfying, from a revenge standpoint, if the 'someone to make war on' actually had something to do with the terrorists. The Israelis, for example, are surrounded by countries that 'harbor' terrorists, and are therefore good war targets. This is a situation that delivers superior revenge payoff. Unfortunately, it again has the practical disadvantage of creating more terrorists. Attacking Lebanon is particularly unwise since many Lebanese are either sympathetic or indifferent to Israel. Bombing Beirut because there are members of Hezbollah there is like a Minute Man bombing Houston because there are undocumented Mexicans there.
It's hard to escape the conclusion that making the injured parties feel better is a primary motive for making war. No one seems to care much who the victims are (usually children) as long as someone 'pays'. Bombs and rockets are indiscriminate killers--Israeli bombs kill Christians, Hezbollah rockets kill Palestinian Arabs. But everyone feels they're achieving something by 'giving hurt'.
The reality that all sides tend to ignore is that beyond making people feel avenged, war is ineffectual, since none of the combatants are going to go away. Israel is not going away. Hezbollah and its backers are not going away. Hamas and its backers are not going away. Everyone now involved in the killing is going to be there for the long haul. You can throw around all the rhetoric you want about "wiping out" terrorists or "driving Israel into the sea," but it's all just rah-rah. And you can claim to believe the rhetoric of others to justify your own blood-lust. "They said . . . ." "It's their plan . . . ." Everybody talks a lot and everybody comes up with idiotic schemes (how about the neo-con blueprint for a free-market utopia in Iraq?), but none of it is based in reality. The reality is that Israel is there to stay--even if the most powerful nation in the world wasn't its servant it would still be the dominant military and economic power in the Middle East. Hezbollah and Hamas or their equivalents are also there to stay, no matter how many times you "crush" them. There are too many desperate people in the Middle East who have nothing to lose, and too many relatives and friends of the dead, seeking vengeance.
Both sides are suckers for provocation, looking for any excuse to overreact and make things worse for everybody but morticians. No one wants to accept the inevitable--that at some point you always have to make a deal. No matter how much you say it's against your principles or your religion, no matter how much you hate and long for revenge, no matter how much you insist the other side is committed to eternal war so there's no use even trying, at some point a deal will be made. Years may pass, but eventually the taste of blood will pall, the realists will speak up, and everyone involved will look around and realize that while they were busy slaughtering each other the world has passed them by. And a deal will be made.