The point Schneier is making is not that we shouldn't have any fear, or ignore threats. Rather, that living in a free society means that sometimes we choose to

The point Schneier is making is not that we shouldn't have any fear, or ignore threats. Rather, that living in a free society means that sometimes we choose to live with fear, because trying to stamp it out would force us to give up too much "essential liberty". That's what it means to "conquer" fear: to control it, rather than letting it control you. "...the question is how much liberty we’re willing to give up to prevent such attacks." Indeed, that's exactly right. Or, to phrase it another way: how much fear are we willing to endure to preserve our liberties? That question is politically out-of-bounds, because the idea that we should respond to fear with courage, rather than ever-increasing security measures, is not acceptable to politicians (either Democrats or Republicans), the Washington press corps, etc.