When Sept 11 happened the popular meme for why we were attacked was "Because they hate our freedom." On a strategic level, they're doing a dramatically good job at winning: look at how much our freedom has been curtailed since then. And they can do it without touching an American; rather, the fear of what they might do provokes the U.S. government into destroying our freedom for them.
(A secondary goal for Osama bin Laden was to bankrupt America, something they are also winning at: since 2001 the U.S. national debt has grown from $6T to $23T.)
You are totally right of course, but the public "debate" around these kind of issues is so emotion-driven that this line of questioning is never explored. Humans generally want someone in power over them that will grant them safety and security, and a sense of certainty that nothing bad will happen to them. Any argument that relies on probability and the idea of trade-offs will never be effective in the public square of a democratic society
Suppose I told you that taking bazookas away from people that live in the city prevents bear attacks? You might say that there aren't bear attacks in the city anyway, which would be true, but you couldn't prove it one way or another. Who knows, maybe there would have been one bear attack if people ran around with bazookas shooting up the nearby forest.
Now add in the complexity that terrorism is more like a rate than a yes/no question. What if I told you that taking away bazookas in the city reduced the crime rate? Well, the crime rate in many cities has decreased, but how are those two related? Once again, we're left with a statement that might sound good to some and bad to others -- and no way to reasonably discuss it.
The only thing we can say with certainty is that no matter what we do, terrorism will continue exist. We can never eliminate it no matter how hard we try. So unless we want each new terrorist act to wreak havoc with massive changes on our societies, we're really talking about trade-offs here. How much stuff do you want to give away for a 50% reduction in terrorism? And once you come up with that answer, how would you know if your giving those things actually was the thing that reduced it?
It's one thing when a pubic discussion has reasonable people talking about the various sides. It's another thing entirely when we start injecting these semantic landmines into our conversations. I'm not saying you're wrong or right; I'm saying there is no way to know.