Just think of Rotweilers as the P-61's of the dog world (Dobermans would be the P-38M's -- faster and lighter) at night, the first and possibly last thing you'll see is their teeth
Seriously, I've found the Rotweilers and Dobermans I've raised to be just big cuddle puppies (but then I spend time to socialize and train them). While I would not guarantee the continued good health of anyone who acted threateningly toward me or my wife in the presence of our Rot (number 4 in a series), I've watched the care she takes with my neighbors toddler -- I've watched the toddler pull herself up right by latching on to the dog's ear and pulling (the dog stands there, rock steady with nothing more than a "why me" expression on her face).
I've found that both breeds to be good companion animals and am in the process of looking for my next Doberman (will be #5, #3 died of a stroke this weekend).
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The problem does not lie with the breeds, the problem lies with those people who buy these dogs because its macho to have a "tough" dog and then either fail to properly train/socialize the dog or actually encourage the dog to be aggressive. Eventually, these dogs (rather than the idiots that own them) make the local evening news and another example is added to the "vicious dog" reputation.
Dogs should not be fashion accessories - if you are not going to properly care for one (socialize it, train it, and if it is not good breeding stock spay/neuter it) don't get one.
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Bruce