Most marine mammal facilities use operant condition which is commonly (but not completely accurate) called positive reinforcement. The animals are not "forced to perform for their meals." Even if an individual chooses to not perform a behavior, or perform an incorrect behavior, they still receive their food, just not immediately. No matter what happens, they get all the food that they need, the training sessions (when public, they are performances) just serve to provide mental and physical stimuli while also providing the ability of hands on medical care. The food they receive at these sessions act as rewards and not their complete diets. There are many times when the trainers will just pour the buckets of food into the mouths just for the animals paying attention to them, but the animals will still remain by the side and perform behaviors regardless of food. The performances and training sessions are considered to be fun for the animals. This is commonly seen in humans when people work towards success with little reward besides accomplishing the task itself.
This technique is also commonly used in many terrestrial animals as the training processes in zoos developed from that from marine mammals. If PETA feels as if the marine mammals are forced to perform for their food, then they have to also think that all other animals that are including big cats, ungulates, etc.
Also, this lawsuit is entirely a publicity stunt and I hope that the lawyers for PETA ruin their reputations eventually leading to a point at which lawyers would no longer want to represent PETA.
