Take away his binky.
Give him a second binky. See what happens. Try a third. Maybe he becomes so obsessed with binkies that mass murder isn’t even on his radar.
Shake him. I know you shouldn’t shake a baby, but we’re talking about Hitler here.
Steal him and drop him in the past. Maybe he’ll go after Neanderthals, who are dying off anyway.
Steal him and bring him to the future. Hope he tries to wipe out Martians, who have it coming.
Lie to him about his future. Tell him, “I am from the future, and you are going to blow up the moon!” Tell him it’s OK, who needs the moon anyway. This will keep him busy.
Show him the complete DVD collection of Lost. It might not change his life, but it will broaden his ideas about time travel. Instead of being the first Hitler, maybe he could be the second Smoke Monster.
Go back further in time and ask his great-grandparents, “Does worst-person-of-all-time-itis run in your family?” If they say yes, kill them.
Read him the story about the beautiful baby who didn’t grow up to slaughter millions or have a creepy mustache.
Show him Inglourious Basterds documentary repeatedly.
Buy him a puppy. Pour barbecue sauce on baby Hitler. See what happens.