In the U.S., a group of men recently got puppies and kittens from Craigslist.com for free. They took these animals into the woods, released them, and then used them as target practice.
Even when people do not mistreat animals so blatantly, they pretty much never give them the same moral concern as they do other humans. Heck, most people (me included) eat non-human animals, and we certainly wouldn't go to our favorite restaurant (or any restaurant!) and order a side of human leg with some barbecue sauce (or alfredo sauce, for that matter).
So my point is that no matter how much we love our pets, and yes, I am obsessed with my poodle Emily, and no matter how much we "like" animals in general, there still is this powerful human inclination to perceive animals as lower on the totem pole than humans. And further, there is an inclination to perceive humanity as distinct, and special, from other animal species, despite pretty much undeniable evidence that we are in fact, animals. (sorry to shock some of you with that news).
Research suggests an interesting reason why people need to perceive themselves as unique from animals, and why in turn, people are less concerned with the moral treatment of non-human animals than human animals: fear of death.
From the perspective of terror management theory, humans do not necessarily cope with death fear by doing the safe or healthy thing. Instead, they cope with death awareness by investing in systems of meaning and value (culture, religion) that give their life purpose and significance, and that in a sense, provide symbolic immortality. Sure, we all know we will die, but that stings a little less if we know that we have contributed to something that extends beyond our own life, and if we perceive that we have lived a valuable life.
One way in which humans gain self-esteem, importance, and significance, and hence assuage mortality concerns, is through raising themselves above the status of other animals. For instance, mortality reminders have been found to make people perceive that they are unique among other animals, to have less moral concern for animals, and to attribute fewer thoughts and emotions to animals — even to pets! (note: in some cases, this is only true when people are primed to think about human-animal similarities as well as death). (see work by Jamie Goldenberg, University of South Florida)
Mortality reminders have also been found to cause people to perceive people from their own country (but not others) as more different from animals, and moreover, to become more negative and hostile towards women displaying their "creaturely," animalistic ways, such as posing naked while pregnant (Demi Moore), and to psychologically distance from their physical bodies (elements of which are animalistic). For instance, death reminders cause people to become less physically active (to do fewer pelvic thrusts) and to become less interested in genital pleasure, but not romantic love (which is perceived as unique to humans). And lastly, death reminders cause people to become more negative towards the idea that humans evolved from other animals.
In summary, humans almost always perceive themselves as seperate from animals even though biologically speaking we are animals. And, interestingly, this powerful tendency stems in part from the need to cope with a deep rooted human insecurity: Death!
When someone harms an animal, they might just be attempting to cope with their own deep rooted fears.