Do you get mad at a parrot for not being able to have a uniquely nuanced conversation with you?  No you don't, because it's not capable of talking to you like a fully functional human being of moderate intelligence.  You typically should get mad over things for which someone is able to be responsible for.    Tigers are kept in cages because a tiger is going to behave like a tiger.  It's dangerous by its own nature.  A tiger mauling someone is unusual only because strict precautions are taken against this from happening out of a clear understanding of what a tiger is and what it can do to a person. So why be mad at someone who can't function like a normal person?  Just take proper precautions.  There's no reason to abuse them by making them fat or malnourished as you're suggesting.