It raises no ethical dilemma at all. The base presumption is that you know what he did, and that you can travel back in time. Of course killing him is the only possible thing to do.
To make it into an ethical dilemma, you have to postulate that you can change the course of history without Killing or seriously damaging him. The suggestion that there is any other possibility, aside from killing him, has not been advanced.
Accepting the premise and the stark choices offered, there is no other reasonable course of action than killing baby Hitler.
This is supposed to be an actual photograph of him as a baby.
See, he’s pretty cute, looks a tad confused but it would be hard to kill that being, no matter what you knew. But, I take your point, as does Jeb (and I’m not making fun), the point would be: you gotta step up.
Luckily none of us will really be faced with this choice and I think it is a valid concept that despite all the evil he did, wiping out Hitler would not guarantee peace on earth.