I voted no, because I don't think it'd be right to kill a kid whose ideas haven't been formed yet. It'd be better to take the child and educate him so that he was a little less... extreme... in his views. He might still need psychatric treatment later, but it'd be better than indiscriminately killing a child who was (at that point, anyway) completely innocent.
A story I heard about did this in the form of some scientists cloning Hitler, then showing the clone lots of Nazi propaganda and leaving him in a room with a Jewish girl and a revolver. They hear a gunshot and go back into the room, only to find that the Hitler clone has shot himself because he couldn't handle what his "brother" had done.
I suspect that's what might happen if you raised Hitler "properly" - he'd likely be horrified by the ideals he was so enthusiastic about...
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Why so serious?