That’s precisely the premise. In doing nothing, we say everything. By doing nothing we show the world that we won’t be dissuaded from our principles and convictions. We show the overwhelmingly large majority of Muslims (like 99.9% of them) that we know their religion is being hijacked by extremists, but it’s not the religion itself causing terrorism. We show people who differ from us that we don’t care about our differences and aren’t scared. Locking yourself in may “protect” you for the short term, but it creates more enemies until that scale is tipped out of our favor.
There were almost 40,000 deaths on US roads in the last year — how many died from terrorist attacks (or inspired attacks)? It’s not even close to reaching those limits, however. There haven’t been 40,000 deaths from terrorist attacks on American soil in all of American history combined. It’s a hugely overstated problem, and while getting worse it isn’t because we’re too lax here at home, but because we’re too busy creating opportunities for terrorists to thrive overseas. Enemies need something to oppose, and we’re giving them plenty.
As for Vietnam, that’s a completely different scenario. Doing something created the need for something else to be done. In fact, by pulling back we were going back to nothing.
Our incessant need for action creates more issues than resolves them. We just act for the sake of it, because we were told to always act, and almost never do we understand the broader implications of our actions — we’re far too short sighted. And any action we take will be fruitless, there isn’t a good answer other than to keep fighting for the values we uphold (or say we do) by not allowing it to change who we are.
If we do make changes then we’re more vulnerable than ever — because we will have shown that they control our actions through their own, they will see that they can get a response from us quite easily. I would rather be in control, than give it up.