You've brought up some really thought provoking points here. If the current strategy doesn't work (and it doesn't), then alternative solutions have to be brought on the table. But war has been replied by war ever since. It'll be hard to achieve a paradigm change on a global level.
I couldn't agree more on your very last statement. These movements and their followers are a true threat.
You're right, the problem is war has always been (and probably will always be) the response to acts of war. And on some level, it's easy to see why. People talk about how violence doesn't solve violence but then how are we supposed to respond to acts of terror/war? What happened in Manchester is an absolute tragedy but now what do we do moving forward? People are not going to just forgive acts of terror or respond with peace when innocent civilians are killed. So we have to find a way to hold those responsible accountable without launching ourselves into a war that only ups the ante. We just don't think long term; we see our people die and demand revenge which just contributes to the never ending cycle.