OP, if you are looking for food for thought, here is my take. I just finished reading Sea World letter on their webpage (their response to all the recent controversy), and I agree that it mostly did not change my opinion on orca captivity, their history with Killer Whales, or the Blackfish move. And this is what I think of all of that: Blackfish was a bit manipulative, but it seemed to be mostly factually sound. I give the movie props for having one person in the documentary advocating for Sea World, to get that balance of opinions.
I DO think Blackfish was important because it finally put a big spotlight on a practice that has become outdated and backwards (displaying orcas for entertainment and keeping and breeding them in captivity); and sometimes that is what is really needed for change to start (as we are seeing with all the protesting, discussion, and celebrity opposition); BUT I also think that it is not fair how it paints an evil image of the professionals at Sea World. There are many conservation efforts, rescue missions, educational initiatives, and research projects that Sea World should be proud of. And most of the trainers and vets probably do have love and concern for the marine animals and do the best they can within the limitations of captivity. But what Sea World is still missing from their conversation is the fact that their best is NEVER going to be enough because orcas simply do not belong in captivity, even if it supposedly garners an appreciation for marine life and helps with orca research.
As for as mistreatment goes, it is possible that the orcas do not receive enough stimulation in their environment, and it's also possible that the mothers and calf orcas were separated from each other; I think it should also be noted that in a few of these instances, from what I've heard/read, the mother was acting out aggressively at the child and the separation was necessary for the calf's well-being. I agree though that in general, this kind of separation should not be happening.
Finally, I think that the response Sea World gave was just too vague and didn't accomplish much. They mentioned "restaurant-quality fish" as the diet of their orcas, but this has already been dismissed by critics because that term doesn't really mean much when in reality orcas in the wild have a much more varied diet and the orcas in captivity have to be fed gelatin and supplements. The article also mentioned that whales are sometimes moved for "heathy social structures". I'd like to know what that even means to Sea World, because I seriously doubt it resembles the Pods of the wild. Furthermore, the article states that their orcas' lifespans are the same as those of the whales in the wild. However, they conveniently left out the fact that many orcas in the wild can live into their 60's or 70's even if many don't.