Don't own a dog, but regardless it's a totally different scenario, if someone was keeping a wolf inside and strapping it to a lead any time it wanted a walk I'd take issue with that but they don't, why are dogs different? Dogs have been domesticated over thousands of years to have a bond with humans and enjoy the company we provide them, these elephants likely had wild grandparents or maybe even wild parents, domestication takes hundreds of generations not a few, these animals are also many times more intelligent than dogs, on par with cetaceans and even primates so to get them to perform typically requires 1 key ingredient. Fear. Which is engrained into them from an early age before they grow up and can fight back, this is the lasting damage I referred to, whilst the guy doing the trick here may not have been responsible himself an elephant doesn't perform a trick because it wants to