For the record, the solution of putting the whale down isn't a judgement against the whale...they aren't "evil" for killing, they are natural, as I think we all agree. But I don't see a huge difference, at least morally speaking, with putting down Willy any more than shooting a cougar that keeps encroaching on human settlements and attacking, or, for that matter, taking anti-bacterial medicine. Two things set it apart, principally...a sort of anthropomorphizing orca-love that makes us love to put these animals in cages and teach them tricks and imagine they are peaceful doves of the sea, and as keeps getting mentioned, $$$. I would say the former is a myopic view that denies a wild animal its natural wildness and really is only self-delusion, and the latter, well, in a cold-hearted way its very practical admittedly, but rather insulting and degrading to the families of those that these animals (quite naturally) kill. Obviously if that trainer had (perhaps even accidentally!) killed that orca the company would be much more likely to fire her than they are to get rid of the attacking whale, and although that's a silly analogy, the point is to the bean counters, the whale is vastly more valuable than the human.
EDIT: and if there is a good way to quarantine the animal without killing it, that's great! I certainly wouldn't advocate killing the animal as some sort of misguided "revenge" for taking a human life, I just want to make that clear!