The whole thing is disgusting. These beautiful creatures are meant to be in the ocean, not confined in an aquarium for our amusement.
But then the polar bears will eat them (see post above). Aside from that, I do understand where you're coming from. At least we're far kinder to animals in zoos/aquariums than we used to be. When I was a kid, you'd see a panther and it would be in a small cage - now they at least attempt to make a halfway decent habitat.