I'm getting kind of nervous now. I used to be so certain that it would be a good idea to go back in time and prevent Hitler from taking power. But now... I can see all kinds of things that could have been worse if he hadn't been there. Like Russia conquering Europe, and America remaining fairly weak, impotent, and economically unstable because we didn't get involved in the war. Although, granted, it's possible that we would have joined the war against the Russians and history would have gone similarly... the Russians might have been too strong by the time we got involved. Or perhaps communism or fascism would have taken root in every country on its own eventually, had it not happened.
There are a lot of things to think about here... how it's easy for a person to be very human and good in some ways, and very inhuman and evil in others. It should definitely teach us to be careful when judging what is necessary to protect ourselves from others. How thin the line is, between humanity and madness.