You can’t go back and kill Hitler as a child because you wouldn’t remember it if you did...............
Imagine right after you invent your time machine you get a note from yourself telling you must use your new time machine to kill an Australian baby you’ve never heard of. So you go to Melbourne in 1889 and destroy world history because of your bad handwriting.
You shouldn't do that even if you could. It's wrong to kill a child. BUT . . . if you wait until he's a teenager . . well that's a different story.
“You can’t go back and kill Hitler as a child because you wouldn’t remember it if you did...”
Rather ... just because you cannot remember doing the act does not mean you didn’t do it.