It seems to me that you're making a colossally important point here - and I appreciate the gracious way you have put it.
You write that "unless you are a survived victim or lost someone to a terrorist encounter, how can you even pretend to understand what they felt?".
It's absolutely the most central question you could pose about my novel, or anyone else's for that matter. Certainly it's a question any fiction writer needs to have an answer to before taking on terrorism as a theme. My answer is that first of all there two basic things a writer needs to get right: to be respectful to the real casualties and survivors, and to accept that one is not speaking on their behalf.
Given that those two criteria are met, one can move on to the question of whether a writer of fiction can contribute anything constructive to the debate around terrorism that could not have been achieved through non-fiction. My answer is yes, and for three reasons.
First, the real survivors are not necessarily inclined to write at length about their experiences. They're not necessarily good at it either. They deserve our support, our understanding, and our attention. Do they deserve three hundred pages worth of our reading time? Only in rare cases. I was lucky enough last weekend to meet one of those rare cases, Professor John Tulloch, who was badly injured in the Edgware Road bombing in London on 7th July 2005. Professor Tulloch is an extraordinary man who has written a book ("One Day in July: Experiencing 7/7") of great power and insight about his personal experience of a terrorist attack. He is both a survivor and a first-class communicator, and this is an extremely rare combination. I think Professor Tulloch would be the first to agree that his survivor status gives him a unique perspective on terrorism, rather than a monopoly on its representation in writing.
I would suggest that only good writing deserves good reading time, regardless of its provenance. I think if a writer feels that they can effectively communicate something of what is lost and gained by the human heart in a time of terror, then they should not be deterred by any misplaced notions of reverence from having a go.
Second, I would argue that fiction performs a valuable office of intermediation between the theme of terrorism and the survivor of real terrorist actions. The effect is to shift the emphasis from the personal to the universal in such a way that the reader can imagine the effect of terrorism on their own life, or can debate and disagree with a point the writer makes much more readily than they might disagree with a real survivor. If someone who has had her family killed tells you she is full of rage, then you just have to accept that. If a fiction writer presents you with a character who has had her family killed and who is full of rage, you are permitted, and even duty-bound, to question whether there might be an overemphasis on rage. You can explore rage, and decide for yourself whether rage is an appropriate or helpful response in this character's situation. In this way fiction lets the issues around terrorism be debated in a safe environment, once-removed from the world of real, fragile lives.
Thirdly, finally, and perhaps more esoterically, I suggest that there is a level of personal truth that both fiction and non-fiction can achieve. This is the truth that resonates with the reader when they look at a character's actions and think, yes, that is what I would have done, or yes, that is how I would have felt. Sometimes it is empathy, rather than strict accuracy, that a reader is looking for.
Of course I fully agree that empathy on its own is insufficient, and anyone who builds their world view entirely on the basis of what they read in fiction will be a strange character indeed - who someone should probably write a book about in fact...