I was waiting for a nod towards the Derek Parfit paradox: The idea that even if avoiding WWII would have made for a better course of history from an abstract ut

I was waiting for a nod towards the Derek Parfit paradox: The idea that even if avoiding WWII would have made for a better course of history from an abstract utilitarian point of view -- a world with less suffering and more pleasure -- it would be ethically problematic because virtually none of the people who are actually alive today would exist in the alternate no-Hitler scenario. People who actually exist are more valuable than people who only potentially exist (it is difficult otherwise to explain the vast moral difference between a couple deciding not to have a child and having a child then painlessly killing her). Unfortunately, this seems to justify everything since (especially if coupled with chaos theory) we can prospectively say of the future that the set of people won't be the same at time X -- say, a hundred years hence -- if we don't go to war with Iran. N.B. That this only form of justification can only work if you are not planning to annihilate everyone on the planet.