Bullshit. There are such things as bad animals, just like there are bad people. It doesn't ALL depend on their "upbringing" and environment. Some animals are just plain old douchebags, just how some people just end up being killers.
People like to cry about horses being sent to mills and butchers, that all the pretty ponies should be saved. What they don't realize is that most of them are horses that will fucking stomp your kids to death and rip your face off their teeth just because they goddamn feel like it. Those animals don't give a shit that you've fed them every damn day and made sure they had a pristine bucket of water to drink out of. You can try to work with them all you want to "rehabilitate" them, but there's nothing to rehabilitate if that's just HOW THEY ARE.
Same goes for dogs and cats and goldfish and every other breathing, feeling thing. We've had animals around the house who, despite being treated kindly and having never been mistreated, have to be destroyed because they were just too dangerous to have around. One dog was even "saved" by someone else who thought they could do something better only to end up destroying it anyway because she kept eating her puppies and tried to eat one of their children.
I don't think "luck" had anything to do with that at all.