However, without WWI, and WWII, war would probably not be hated as much and seen as a futile and wasteful thing to wage.
That's an interesting point. I've thought about WWII before and the more I think about it the more it almost seemed bad but necessary.
At the time, terrible, but in the long run perhaps it was for the best.
Look at all the new technology developed in WWII, like rockets. It broke up the empires (or didn't WWI do that a bit already...) or at least broke up the British empire, and you know, maybe it was good to get all that racism out.
Maybe without all the racism and racist killings the Nazis did, racism wouldn't be frowned upon so much and racists wouldn't be compared to Nazis not to mention how horrific it was, hopefully the world learned a lesson from it. Though World War I should've done that before.
Hmmm... either way, given a time machine, I'd be careful what I'd erase, you never know what going back in a chronosphere to erase Hitler would cause. Like Russia invading Europe like in Command and Conquer Red Alert.