I agree that killer whale's shouldn't be kept in captivity, but than on the other hand, I also love me some bacon. Pigs are also sentient creatures with high intelligence yet we see them as a food source, and thus don't really care about their conditions in captivity.
But we should. Future generations will judge us very poorly on this.
Generally, I find such speculative statements worthless. It's another way to say "I really think this should be obvious and that my idea will eventually be widely accepted to be correct". That's all well and good, but everyone thinks that about their own thoughts. It really doesn't contribute anything to the argument; it's an attempt to shame your opponent into agreeing with you by invoking his future childrens' potential disdain.
I also think that if you really want to know what future generations will think of something, you should refer to what prior generations thought of it. By this standard, future generations are likely to taunt us mercilessly for caring so much about what we imagine to be a whale's internal monologue.