People who do shit like that will also do that to people. A bunch of serial killers had a history of abusing animals as kids. I say kill them. hmmm, tough way to "justify" that, eh? Then we'd be the killers. What would make us any better? hmmm, I guess maybe we've just got to realize that we live in a fundamentally diseased and insane culture, that person likely suffered an abusive and difficult life, have some compassion. Well, shit, that doesn't work either. You could always be a snitch and use the established power structure to have the dogs taken away, but then they just get taken to the pound to eventually get euthanized, and the pieces of shit will just get another dog. I don't know, just do what you feel is right (and maybe keep your mouth shut about it ;-).
How about kids who ride trains with dogs? You know that loud flange squeal that hurts so much because they're too punk rawk to wear ear plugs (unless they're already deaf from standing next to the speakers at shows since they were kids)? What the fuck do you think that does to a dog, whose ears are substantially more sensitive?
I really hate the idea of "pets" in general. People say they love their animals, and they probably really do, on a superficial level, most likely out of emotional immaturity and ignorance. Our interaction with these animals started because we had left behind good scraps, and we had a similar social structure and cooperative hunting strategies. Domesticated dogs became specially adapted to humans, displaying a well developed emotional intelligence and ability to read our subtle expressions/body language better than chimpanzees can (and seemingly, most people these days). They served a purpose and earned their keep. The vast majority of people don't understand the evolutionary/selectively bred context of their "pet." Sedentary, urban 9-5'ers buy a "working breed" keep it in an apartment all day, take it on a couple walks, and wonder why it tears the fuck out of all their shit. People treat their animals like toys, even if they really do take care of them, it's rare that someone actually gives an animal everything they need to be healthy (especially by feeding them shitty, grain based "food." Cattle aside, how many wolves do you think farmers killed to keep them from eating up all their corn and soy crops? Why did my beloved dog when I was younger get liver cancer?)
Fuck, I could go on, sorry for the rant.