No, I wouldn't kill Baby Hitler. I'd instead wait until he was about in his mid-to-late teens, but I still wouldn't kill him.
Why, you may be asking? Let's travel back in history and learn about how he became what he was shall we? Now, I'm not a history buff by any means so my details might be a bit off if not flat out wrong...
If I recall, the main reason Hitler came under such intense hatred for Jews is because his mother died while the care of one (and yes, I meant to word it like that). But check it out: to my knowledge, Hitler's mother suffered a brain hemorrhage or aneurysm or something of that nature, and the young desperately sought to find a doctor. By the time he did however, the doctor in question just happening to be Jewish, the damage was too extensive and the doctor couldn't really do anything. Longer story abbreviated, Mother Hitler dies, Young Hitler snaps, blames Jews for everything, the Holocaust kicks off, so on and so on, or something like that.
Taking that into consideration (and after cramming as much German into my skull as humanly possible), I'd visit him, maybe even console him. Who knows? Maybe WW2 would never have happened (or at least Germany and perhaps a few other Axis countries wouldn't have been involved). Maybe the world today would be a much simpler place to live. The possibilities are nigh infinite really.
Just saying.