It's mob mentality. The marine was actually putting the puppy out of its misery; it was sick and, out in the desert with no possibility of water, food, and care it would have just gotten worse and worse and died a longer drawn out death. The guy just did it clumsily and one of the guys with him obviously decided to put it on the Web from his cell phone camera. Because it was a puppy everyone gets all bent out of shape, thinks it's abuse without knowing the circumstances. They normally shoot the dogs. It's our human side that gets anthropomorphic about it, cares "how" something dies.

I remember when I found a baby bunny my cat had gotten to outside and torn a small hole in its side and I wanted my husband to kill it, put it out of its misery so I gave him a shovel to smack it with but then carried it around tenderly, looking for the right "spot" trying to find a soft, mossy one. It took several minutes before I realized the discrepancy there, of hitting a baby bunny with a shovel on a soft bed, and realized I didn't want to watch/be responsible for killing the rabbit no matter what. So, I took it down in the woods with some water, covered it well with leaves so the cats were less likely to find it, etc. The next day when I checked it was not there and I like to think it recovered. Probably very selfish of me.