That's what Roy Horn says, but I don't buy it. The tiger that mauled him wasn't "playing", but reverting to type. "Montecore vuz tryingk to save me!" Yeah, sure...save him for breakfast, perhaps.
The reason for that wasn't that he was afraid that they'd actually attack him with the intention of doing him harm. Rather, the reason was that they were such immensely powerful animals that one swipe was quite capable of snapping his neck, even as a matter of play.
Horses and cows are stronger still. Potentially dangerous, yes, but we trust their temperament in situations where we could never trust a trained wild animal.
Given that, I hesitate to imagine a "pet" bear in a playful mood.
I don't imagine that domestic grizzlies would be used as lap animals. I imagine them loping around a car dealer's lot at night, or pushing concrete barricades into place, or running down a perp.
I have to say something about cats. I have two that hunt. Both bring their catches home to show us, and since they have a kitty door, they bring them into the house.
One of them is of the "eat the best part and leave the rest as a offering to the big mother cat." The other seems to believe in catch and release. Catching and killing are two entirely different activities for a cat.
Not that it matters if you're eight feet tall and weigh 800 pounds.
I think there's a cube law problem in the case of Roy's injury. The force needed to pick up an adult human with a mouth full of teeth is quite a bit greater than the force needed to pick up a cub. Roy was just too big.
Even if the cat was in meal mode, there's a difference in the ways cats behave when they are killing. It's quite definitive.
"We"? I dunno about PA, but the days when herds of cattle and horses roamed unsupervised amidst the gently rolling hills of Northern Virginia are basically long gone, if they ever existed in the first place ;)
More seriously, we keep those sorts of animals contained for more reasons than just to keep them from hitting the road. Horses bite and kick, cattle charge, and that's partly why we keep them behind fences these days. Even trained, domesticated guard dogs are not simply set loose on the dealer's lot overnight - if they're not directly supervised and restrained by a handler, they're contained, and a bear will require a bit more in the way of "containment" than the chain-link fence that holds the Rotty in at night.
By that same token, police dogs are restrained by a handler who is generally a large fellow, capable of holding the dog back with a leash, even when the dog would prefer to charge in and attack, but I don't foresee the police departments finding officers who can successfully restrain a bear on a leash. Oh, sure, I suppose you could build some sort of mobile pen to haul the thing around, but even if you did, a police dog is highly unlikely to kill a perp before the handler can catch up and restrain it. A 500 pound bear, OTOH, is far more likely, I think, to do such a thing, whether accidentally or not. Police dogs chase perps because we've leveraged and redirected their natural prey-chasing instincts - I'm not sure that this is wise idea with bears, especially not when simply knocking over and stepping on suspects is enough for the animal to accidentally kill someone.