People like that have something wrong with them.
Some people just never make that connection to the rest of humanity. I think it has to be made in early childhood, or not at all. If the connection is never made, the moral code that normal people live by doesn’t make any sense to them. They try to make sense of it using the only thing they know, utilitarianism. Because to them, people and animals are mere objects to be utilized. It’s sad.