I have a large breed dog & a small child. (The horror)
Prior to owning her, we put a lot of research and time into finding the right breed & right dog for us.
The breed I chose, are known for:
Being loyal, even tempered and devoted. They are low energy dogs that like to lounge around, but enjoy playing. They are known for being good within family settings, and socially (they're good with other people and other dogs).
Once I got her, I put all the time I had into training her, not just the basics either, when you get a puppy/dog, they need socialising in all types of ways and desensitising to a lot. So as soon as she had all of her injections and the vets said she was ready for walks, I did everything I could to ensure a behaved and well mannered dog, I made sure she experienced every situation she could.
I walk her everyday, with my little one in the pram, she walks happily besides us. I never let her off the lead, but she's very 'polite' to every person and other dog we meet. I'm often asked by people if they/their children can stroke her, I often explain to them the correct ways to greet a dog, she will also happily 'sit' and 'shake a paw' for them too,
At home, she's lovely too. We have boundaries in place, she isn't ever left with the little one (because I'm not stupid), but she has her own bed in her own space and she's very well behaved.
She had that many experiences and stuff as a puppy, that now as an adult she's very easy to manage.
I know people who have dogs that are terrified of prams - because they were never exposed to prams as a puppy.
I know people who have dogs that get excited and chase anything that moves, why?? Because as a puppy they were only walked in quiet places and didn't have the chance to 'get to know' certain things or situations.
The list goes on of course.
Now, my dog is a dream - this is simply down to me choosing a breed correct for my lifestyle, and the fact I put the time and effort into training her (and not just as a puppy, training doesn't stop, you should always continue to positively enforce all training with all dogs of any age)
However - if the same dog was thrown into a lifestyle that didn't suit them & then had owners that didn't commit to training them and did not correctly control their dog, it would probably end in disaster.
_
There's also the fact that certain breeds attract certain people, the breed of dog I own for example, all other owners of the breed that I know, also have children and the time to suit the dogs needs.
So if there's a particular breed that attracts the wrong sort of person, then it's going to end in disaster. Especially when said breeds were not bred for the lifestyle they are given and needs are not met. That's probably the reason why that statistically, it's always certain breeds more than others that end up in bad situations.