I don't understand why people say things like that. If you think it's bad to own blood parrots, then you must also believe that people shouldn't own dogs or cats. When you stop and think about it, dogs and cats were hybridized for our amusement, and a dog or cat wouldn't live as long in the wild, so would you say that it's wrong to own them?
He's not saying we shouldn't keep them, he's differentiating between keeping animals for the animal's well-being and keeping them for our own pleasure. It is impossible to draw the line where modifying the behaviour/body of an animal is "right or wrong". From an biological/evolutionary perspective, killing marine fish by keeping them in freshwater is no different than keeping them in ideal conditions for their entire lives. both have been prevented from propagating the species.
Regardless of how big your aquarium is, or how well kept your fish are, unless they are breeding you are compromising the fish's health and natural behaviour, for your own amusement.