That's the take from ABC News:
What, then, provoked one U.S. Marine to let himself be videotaped apparently flinging a yelping puppy over a cliff, bursting into laughter at the sound of the animal's body hitting the ground below? The tape of the apparent incident has rocketed around the Internet, provoking a firestorm of criticism. The motivation for such an act, if it did indeed occur, may be as complex and deep as the U.S. war that has dragged on for more than four years, experts told ABCNEWS.com. Chief among them: Having to live with the constant fear of being injured or killed might have led this Marine to take his aggression out on a defenseless animal, several psychologists said.
I'm not convinced the tape is real, or more specifically that the puppy was alive. Either way, the tape is a disgrace and all involved ought to face serious consequences. But still...this is ridiculous. The Danger Room's Sharon Weinberger offered the best explanation:
I'd also hesitate to make a political point about how war dehumanizes people, which is of course true, but doesn't necessarily explain why someone would toss a puppy off a cliff. Teenagers across America have been doing sick stuff to puppies and kitties for years. Guess what: suburbia dehumanizes, too. So, assuming the video isn't faked, the guy may have thrown the puppy off the cliff because war dehumanized him; he may have tossed a puppy off the cliff because suburbia dehumanized him; or maybe he and his buddy were just a couple of heartless idiots with a camera. Take your pick.
Which is to say--it's impossible to know what motivated these Marines to throw a puppy off a cliff, or if they did at all. And this wouldn't be the first story of U.S. soldiers killing dogs that turned out to be a publicity stunt.