Cetaceans are complex, intelligent animals. They have social habits and methods of communication that are developed and used for their survival in the wild. Captivity is not only a limitation to their freedom but also to their ability to be social. The methods used to capture marine mammals are inhumane, resulting in injury and often death. For creatures that use sonar for communication, cement pools are a stressful and severely limiting environment.
There are many, many more reasons why it's unethical to keep marine mammals, and more specifically cetaceans, in captivity. Please educate yourself: http://www.humanesociety.org/assets/pdfs/marine_mammals/case_against_marine_captivity.pdf
It's possible that Justin Bieber is unaware of how his actions influence his audience, but it's time for him to recognize that this new generation demands to be shown reality, no matter how ugly it is. Justin Bieber, please use your influence to help us shut down mammal aquariums instead of encouraging their inhumanity.