They would still be dangerous, they just may not kill whoever feeds them because they're smart enough to play the long con of being fed regularly by a human, than eating said human and having to scavenge for food on their own. You scare it, though, and that all changes.

Natural Instinct is something which can only be bread out of animals to a point. They are hard wired to do what they do at a certain level. Humans have been domesticating dogs for millenia and yet my 4 kg (~9 lb.) toy poodle still insists on peeing on stuff as an assertion of dominance, the same way his ancestors did.

He doesn't think about it. He doesn't have the capacity to ponder the utter pointlessness of pissing on random objects. He doesn't realize that he's a scared little baby who is one level above one of his stuffed animal toys on the food chain. He attempts to assert his territorial dominance by urinating on the world because that's what dogs do. It's hard wired into to their DNA.

Think of it another way. If you've ever had a house cat sink it's claws and teeth into your arm, whether it's playing or being aggressive doesn't necessarily matter. It still hurts. Now imagine the cat weights 204 kg (450 lbs); about the size of a tiger. The seriousness of the situation increases from minor to life threatening.

And yet, there are an alarming number of people, in the United States alone, who seem to think having a pet tiger is a good idea. Ok, so it knows it's "owner" and is familiar with them. It would never harm them, would it? If you can reason with my house cat as to why it is illogical for her to randomly attack my arm and bring her over to the sensible side, I'll be more open to arguments from people who think they should be allowed to own tigers.

There are a multitude of arguments to be made as to why raising large, wild animals for pets is a bad idea. Beginning with, a bear is still a bear. Even if it's a friendly bear.