Think on this.

To the question, "If time travel were possible, what would you do?"
Many answer they would go back in time and kill Adolf Hitler.

And if you look into it, Adolf survived MANY assassination attempts.

Further, if you are able to look at multiple time lines, there is always a Hitler.

There are even people who talk about time travel, and the attempts to kill Hitler.
No matter what they do, or who they kill, there is always a Hitler.