IMO it would be a VERY BAD thing to kill Hitler in the first place, or anybody else in history for that matter, if anybody had the ability to travel time and they changed the past, it WOULD affect the future, Ok , Ok so I don't go back in time and kill my father and I still get born right? Well........maybe not, what if I prevent the death of a man who would grow up to kill my father? That might be a minor little problem when he kills my father before I am born.or if I see my mother BEFORE she meets my dad and cause her to NOT marry my father...........on the same token, what if I killed Hitlers best childhood friend by mistake? or if I goofed up and lost the plans to a nuclear bomb and the third Reich found it. or the worst case, and they killed ME, and took my machine and came into the future and got the tech we have now?
Changing history.........Bad Thing
Learning from History....Good Thing