I think the point of the article is animal rights activists who go overboard anthropomorphizing animals and deciding what they must want. Who knows what Keiko wanted? Maybe he felt the human caretakers were his parents and abandoning him in the ocean to be "back in the wild" is not what he really wanted?
Imagine some space aliens decide that your life of comfort with a job and a house is a "prison" and what you'd really want to be doing is hunting and gathering in the jungle, so they pick up you up and plop you down in the middle of a rainforest.
My dog would be unable to survive in the wild and he seems to prefer the company of other humans, not dogs.