Should Mammals be kept in Captivity?

I believe that Mammals shouldn't be kept in captivity. The reasons why are because Mammals need to bond with their family in the ocean(pods),they perform tricks that are exagerated variations of their natural behaviors, and in the wild dolphins are predators and at Sea World they are given food for a reward.
Mammals need to be in their natural habitat so they can bond with their families and learn to protect eachother from any other dangerous mammals in the ocean. Mammals shouldn't be kept in captivity because thee human interaction in captivity increases the risk of transmitting diseases to the animals.
Mammals perform tricks that can be dangerous to us humans and are out of their natural life in the ocean. The best way to learn about these mammals is observe them in their natural habitat instead of learning about them in captivity because they can become dangerous to humans when they interact with eachother.
Wild dolphins are being treated in an incorrect way. The reason why is because Dolphins are use to hunting for their food in the ocean and they are loosing their predatory sence.They are in a small tank, wich means that they don't have much freedom to swim around. These dolphins are being fed popcorn,french fries, breadby guest wich can cause instential injuries,poisoning and even death.
I believe that animals should not be held in captivity now and in the future. I know that for a fact no human being would like to be in a cage all day. Perhaps maybe only have an hour to swin around and be free because the mammal is doing a show and putting money in a persons pocket who obviously is not one-hundred percent ok and smart in regards to let animals be free and not captivity.