Case? Kind of weird. You presented a hypothetical dog with hypothetical behaviour issues, declared that no amount of training would solve the issue, based on nothing more than your unfounded fears, and you think you made a case of some kind? Out of curiosity, were you trying to make a point against owning dogs as pets? BTW, back at work.
Look if you really find it impossible to live without a dog and determined to get one, even though there's an (albeit slight) risk it will one day attack one of your kids, then ffs stop posting nonsensical remarks - just go ahead and get then bloody thing.
I have to say, I've never seen anyone get so worked up over somebody else getting a puppy. Plenty of people have had dogs all of their lives since they were children and have never been attacked. In fact, I would venture to say that more people have not been attacked by dogs than have been attacked by dogs. Some people probably should not own dogs because they are abusive or negligent, but the OP doesn't seem like that type of person. People kill other people too sometimes, shall we discourage people from having children because the child could possibly kill somebody one day?
Never, and I do mean never, leave a toddler alone with any dog, large or small. Too many have and regret doing so for the rest of their lives.