I dont understand your arguement that it would be more human to kill the whale. You cant blame a killer whale for doing what comes natural to it. As for not displaying animals and that its "sick", if we applied that logic to all animals then we shouldnt raise cows for beef, we shouldnt fish for food, keep dogs and cats for pets. Robb would not be able to make his hot wings.
While Sea World exhibits fish for profit, they also use the profits and the interaction as research to save and help all sorts of marine life. Many of us would never have the understanding or the care for these animals if we hadnt seen them at Sea World. With the "release all of them" logic we wouldnt know about these wonderful animals until greenpeace rams the Japanese boat that killing them with no disregard to future populations. There is a lot of good that comes from their research as well as what BGA does for African animals. There is no difference in my mind between the value of a whale or a horse or a dog or any animal for that manner. There is always going to be danger involved with working with animals, and the trainers at the parks know this above all else. I for one think the benefits far outweigh the negatives.