Uh, humans in prisons are criminals. They committed a crime. The animals in captivity aren't criminals. Animals can't be criminals because they don't have the capacity of reasoning.
First of all, I think PETA actually attacked Disney's Animal Kingdom at the beginning:
"Even in planning stages, various Florida based animal rights groups and PETA did not like the idea of Disney creating a theme park where animals were held in captivity. The groups protested, and PETA tried to convince travel agents not to book trips to the park"- This was taken from Wikipedia.
Finally, can someone that defend SeaWorld with passion remind me when was the last time that an animal KILLED a cast member in Animal Kingdom? We are not just talking about the cruel treatment to animals but we're also talking about human lives who are endangered. It is normal that 3 trainers died at SeaWorld? Fact: It is NOT.