It may sound crazy to you, but yes you do actually stand a greater chance of making peace with enemies and therefore reducing attacks from them if you stop shooting at them and bombing them and ask them kindly why they are flying planes into your buildings and then make a good faith effort to address those issues.
You're right, it sounds completely crazy to me. Nobody really bombed or shot Timothy McVeigh. Or the RAF. Or the Brigate Rosse. They did all their shooting and bombing all by themselves, at the cost of hundreds upon hundreds of innocent lives. It's not that the questions of causes or morality of our own actions are illegitimate - they aren't. The idea that we're going to practically stop amoral nutjobs by just being ever so much nicer seems based on nothing but wishful thinking, though.
Evolving beyond being amoral nutjobs ourselves is the first step to eliminating amoral nutjobbery elsewhere. There's a lot of extra work that needs to be done on top of that, such as good-faith social programs to help their society recover, etc.
I think the point is that you can't stop the amoral nutjobs (awesome term BTW!) by killing them (and their family and friends) either, because that just embitters another generation.
Your examples actually illustrate this perfectly - Timothy McVeigh justified his murdering in revenge for the murdering done at Waco; and both the RAF and Brigate Rosse were driven partly by the injustice of former Nazis (those nutjobs really took their amorality seriously!) returning to power.
I accept that there are psychopaths who murder for no reason, but luckily for our species they are very rare. All the killing discussed above was triggered by severe injustice including murder - revenge. Our civilised societies are practically defined by their rejection of revenge as a reason for anything, replacing it with either rehabilitation or prevention. "An eye for an eye" is the mark of a primitive society (or person) that doesn't understand positive feedback loops.
What do you recommend when dealing with an enemy that isn't interested in your good-faith efforts?
Then you look at other options. But in this case a good faith effort could resolve the problem very quickly. The people attacking the US aren't really asking for that much. They just want the US to stop sponsoring violence and tyranny in their region.
Unless 'other options' encompasses some yet undiscovered diplomacy tack it would escalate back to the status quo pretty damn quick.
Well, the Europeans would just send diplomats around until they could conveniently forget about the problems, as usual.