<I am continuously thunderstruck by the numbers of people who tell stories of surviving the Blitz or tell about the Holocaust, who turn around and say that there is never a good reason to fight a war.

Perhaps you must experience it first hand in order to understand. I suggest that you go to the front line of some battlefield, just to see how close you come to death without getting killed.
After that you will be in a better position to talk about it.

How does one brain contain these two thoughts at the same time?

Did you want the logical, physical, or emotional answer?

I can't talk for others but for myself. I was a small child; I did not provoke the hostility, yet a group of people was actively trying to snuff the life out of me. I still do not understand how anyone in the world, including the ‘enemy’ would have benefited had they succeeded in their attempt. I DO know that the people who were killed would have contributed their special talents to the society. Who knows what that little girl; who’s torn body I observed on the sidewalk, would have grown up to be, perhaps she would have been the one to figure out how to construct a practical single stage to orbit spacecraft, or perhaps she would have figured out the unified field theory. We will never know.

Churchill could have stopped the bombing of London in five minutes by surrendering and saved many lives. Until later, of course.

There is a big difference in defending one’s self and attacking someone. I would not condemn anyone for defending him or herself with whatever means necessary.
I am FOR law and ORDER and I am against WAR and other evils in this world. I am not on Saddam’s side and I suspect that most of the thirty million or so protestors feel the same way. But consider this, IF ALL those demonstrators WERE on Saddam’s side, HOW would the US ‘eliminate them’?
My personal view on this ‘Saddam situation’ is that it should be considered from the same viewpoint as any other crime.
Assumed innocent until proven guilty, is that not written somewhere in the law books?
If he is guilty then sentence him according to the LAW.
You say that he is murdering his own people in his own country, that is quite possible, although, I have not seen newspaper reports on such events. I have seen newspaper reports about murders in the United States. In my opinion, people in both countries should stop murdering their brothers and sisters. I do not know how this ‘ideal’ condition can be achieved. Is WAR the answer? Are the people that kill a killer guilty of killing? What is a human life worth? There are many questions that come to mind about these kinds of problems.
How to handle the ‘Saddam situation’?
I am sure that there are many ways that can be considered. But in my opinion, WAR should be the last consideration.

If you wait long enough, both leaders will die, perhaps of old age.