I love how people just forget that everything can be conditioned to hate. Look at humans, your "normal" one is affectionate and peaceful. However, with proper training they can be ruthless and cruel.
Dogs are no different and if anything, are less dangerous than manipulated humans, since they are far less capable of cunning.
My parents had a Dobberman. The dog loved everybody, she slept on beds, acted like a lap dog, and licked anything that moved and she was friendly with.
If somebody got on her property that was a stranger, she let them know they weren't welcome by barking. If they persisted, she would nip at their pants. If they kept coming, she would grab a shoe. I had friends she was less used to that she would just bark, they didn't show any fear because they knew she was a nice dog and we were around, she never bit them.
In 12 years she bit 3 people. My future wife when she showed up un-announced and early in our dating, a guy who was jogging along the road outside of our property who actually went *IN* our property to kick her because she was being "aggresive" (she never jumped the electric fence). She had a rib broken because he kicked her, but then she ran his ass down and ripped his shorts (never bit him though).
The last person she bit was my brother, she hated flying things and always nipped at them. A fly landed on his leg when he was sun tanning, she nipped at the fly and got him. She was so scared that she ran to a hiding spot and stayed there for hours. When we found her she was shaking.
My dad trained her to be immediately obedient through positive conditioning. Treats instead of punishment. We never taught her to attack anybody. Just to obey simple commands and she never faltered in her obedience. Neighbor kids would come over when we were around and give her treats, she loved them too.
When I get a house I want to get a Dob, my wife says we shouldn't because she is so ingrained by the popular media sensationalizing, even though she knew and loved my dog. It's sad that people are so ignorant, not only of dogs, but of psychology.