That's his opinion, but I doubt seriously he's done any experiments on puppies chewing infant toes. Heck, babies bones aren't that tough - and if you've ever seen a pit bull puppy chew through a pork rib bone - you'd know a couple of toes are jellybeans to him.
However - the new article said the parent's stories were different. Changing stories = lies in my opinion. If they said "I woke up when the baby was screaming and these toes were chewed beyond repair" I'd feel awful for them and that would be it - but that's not what they said, so I don't know what to think.
I do think the vet is just having an opinion, and I think his opinion was pulled out of thin air. So many are.
MOST pit bulls are sweet pets. If it were true that they were all mean, no one would own one as a pet.