Nonsense. Very few dogs, if properly socialized, will attack people, unless trained to do so. This habit of killing family pets every time they enter a house is done to intimidate the humans, and for no other reason.
Socialization is the act of training a dog not to be highly aggressive towards strangers and other dogs. Lacking such training, a lot of dogs can be highly aggressive towards strangers or strange dogs, though it's most common in rural areas where the dogs are around strangers less.
A great many dog owners do little to socialize their dogs properly.
Still, very few will outright attack. Charging up to someone barking and growling, yes, but attacking is much more rare.
Yet we do still hear lots of stories about dogs getting lose and biting people. My brother and I were bit as kids. Once simply because I walked down a county road we lived on past our neighbors. The neighbor's dog had puppies and was apparently decided that being on the road 50 yards from where her puppies was too close so she chased down my brother and I biting us both in the legs while we tried to run. It probably would have been worse but my father came running and drove the dog off.
The old woman who owned the dog came running out and started screaming at my father because he kicked her dog. My bite wasn't two bad. You can barely still see the scars on my brother's leg 30 years later. However all that woman, who had otherwise been a pretty nice neighbor, could see was that her lovable pet was being hurt.
She never forgave us for reporting the incident to county animal control which took the dog and put it down. She never talked to anyone in our family again. People often don't see those they love for what they are regardless of if they are pets of people.
My stepdaughter went to pick out a Christmas tree with her father a few years ago when she was six. There was a dog there that the owner of the lot of trees said didn't bite and she could pet it. She pet it with the owner present, and then they went and got their tree.
On the way out she stopped to pet the dog again. It lunged forward and bit her in the face without warning. It's top teeth sunk in just below her eye and lower teeth under her jaw. Her father got the dog off of her and got her to the hospital. You can barely see the scars on her face now, but if the dog had lunged just a tiny bit higher, she'd have lost an eye.
Now I will agree that it is far, far more rare for a dog to attack an adult than a child. However, when a dog thinks someone it feels bound to is threatened, they don't seem to care a whole lot about the size of the threat. It's a quality that has earned them the name of man's best friend. They are loyal and protective. However, they don't always know when NOT to be protective.
That's often not the fault of the dog, but it's also something that can't be ignored by someone dealing with an aggressive dog.