Hitler was ,in fact, beaten by his father.
I've known plenty of adults my age who were beaten as kids, and none of them turned out worth a damn. No amount of anecdotal evidence will convince me otherwise. Beaten children grow up to be beaters. Sexually abused kids grow up to be abusers. There is a mountain of evidence to prove it.
Every child is born with a clean slate, and there are no "bad" kids; they are made that way by failed parenting.