It really isn't a poor argument because the power to change the past means the power to unilaterally change the present and the future as well. It's naive to believe that the power to change the past is a one way street since every action comes with a reaction ...
It is not out of cowardice that I refuse to exercise such a potential power for preventing the slaughter of millions of human being since it means far more reaching ramifications than you think. Without Hitler starting WWII, racism and colonialism would run far more rampant today than it would today. It is maybe you who is the immoral one ...
Even if you interpreted the question in another way, how would one justify killing an infant that has yet to commit a crime ? More importantly did Hitler commit any other crimes along the way before he came into power as chancellor ? You don't know what the question entails and you haven't given it much thought it either ...
I'm not sure you understood me at all. Destiny is the idea that the future is concrete, static, unalterable. It's a very naive way of thinking about the Universe and its operations, especially given quantum physics and its conclusions on this topic.
So your argument is that it's more beneficial for the world to have undergone Hitler than suffer racism for a few short years? Uh, good luck convincing anybody of that.
If I were aware that this being would eventually be responsible for starting a world war, the decision is quite simple.
Again, in my eyes you are perverting the inquiry. This is the question in my understanding:
Would you, knowing the results of Hitler's actions, kill him as a baby in order to prevent such actions from occurring?
Whether this entails time travel to the past (impossible) or the ability to predict the future (implausible) is not relevant. All that matters is whether you could kill a currently innocent baby to stop a future travesty.