I love polar bears ... but only from a distance.
While true, I'm sure that bears who are raised around humans interact with them differently than wild (and hungry) animals. Even a housecat can be dangerous if not properly socialized when young.
This is true; a "tame" bear will not act the same as a wild one, not having learned wild habits from its mother as a cub. Still, it does not have the millenia of domestication encompassing many thousands of generations that a housecat has... not to mention the sheer size differences. A polar or brown bear can weigh 1400-1500 pounds, and can easily rip a man open with a single swipe of a paw, or crush a man's skull with a single bite. A bear is a scavenger and, above all, a high predator, with all a predator's instincts. A tiger would be a better analogy than a housecat; if the tiger gets hungry or the person behaves inappropriately for a tiger's likes, munch! goes the tiger. Same for a bear. Bears have one of the worst records of "turning on" their keepers; the circus bears and ones performing in places like India typically are smaller, less aggressive varieties, and have had their fangs and claws removed. Often they are kept partially-drugged, and well-fed, to keep them "safe".
The polar bear is widely recognized as one of the most dangerous animals on Earth, and not without reason. That cub, cute as it looks, is doing what comes naturally, and when it gets a little bit bigger, that behavior won't be cute, at all.
Incidentally, there has been a marked increase in spottings of "mixed" polar bear-grizzly bear hybrids, called "grolar bears" or "pizzlies". This is occurring, some say, because of reduced habitats and melting ice packs that are bringing the two species into closer contact, leading to inter-breeding. Experts worry that this process may accelerate the extinction of polar bears, as mixed offspring are often infertile/sterile. Enjoy those white cuties while they're still around to be seen!