The thing is its a tough call to let animals back into the wild after they've been "domesticated" in the tanks, as there is a fairly likely chance their instincts may not be as astute as they need to be and they might not be able to survive. Perhaps even if they found family and communicated with other orcas, they may not be accepted back into the pod. No tank could ever be big enough for a whale, but compared to how it used to be at other zoos and sea parks where they had really bad disgusting conditions, Sea World really does try to have a nice sized tanks for the whales.
It actually disgusts me that the movie (or activists) would suggest not to take kids to these parks, because as a kid I was so fascinated by Sea World and the Shamu. It helped me put into perspective their sheer size and beauty, and made me into the ocean and sea animal lover I am today. Do any of these "activists" even consider the positives and educational experiences provided by Sea World? Do they care about the experiences they would take away from kids and families who might otherwise never see an Orca in real life? Sure doesn't seem like it.
I also think it is important in some aspect for people and kids to be able to see and learn about these wonderful creatures up close like they do at Sea World in order for them to understand and have an appreciation for the ocean and the animals in it. While I can understand some people think there should be no whales in captivity, I think there needs to be an exception for the reasons I laid out, and I think if any company is responsible and caring enough to be able to provide a nice place for them to be, it's definitely Sea World.