I've watched far too many episodes of "Breaking Bad" in the last few weeks, and just about my only defense is that the show does provide lots of food for thought about ethics. Spoiler alert! If you're trying to catch up before the season finale on Sunday, don't read this post.
Lots of people get killed in the show, and many of the killings are done for purposes of self-preservation. The killings make it clear that self-preservation is one thing, self-defense another. You might plausibly say killing in self-defense is always justifiable, but clearly killing to preserve yourself is very often wrong. Take for example Todd killing the boy on the bike. It was a matter of self-preservation, because the boy had witnessed the train heist, but not self-defense (the boy was not on the attack), and the killing was obviously very wrong. When Walt poisons Brock, nearly killing him, that was self-preservation (he did it to get Jesse to help him find the evil, murderous Gus), not self-defense (the boy was not on the attack). When Walt watches Jane die, his rationale had to do with self preservation, but she was not attacking him--it was not self-defense. We may have some degree of sympathy for a person who kills for purposes of self-preservation, but we certainly don't excuse them in the way we do when people kill in self-defense.
OK, strange segue: when it comes to killing animals, we don't make this sharp distinction between self-preservation and self-defense. I can kill an animal in self-defense: if a bear attacks me, I can attack the bear to protect myself. But it's also true, we think, that a perfectly innocent rabbit could be killed, if I were lost in the woods and had to kill to survive. We can't kill innocent, non-attacking humans for purposes of self-preservation, but we can kill innocent, non-attacking animals for purposes of self-preservation. Surely we can. That means that if animals have rights at all, they are not as robust as human rights. They are overridden in cases of self-defense and self-preservation, whereas human rights are overridden only in cases of self-defense (focusing just on those two circumstances).
The interesting thing is that even staunch defenders of animal rights often grant the self-preservation exception, and I'm sure they don't grant it across the board, excusing every killing for self-preservation in a drama like "Breaking Bad." Without putting it this way, they actually agree that animal rights are less robust than human rights. Case in point: in the book Zoopolis, Sue Donaldson and Will Kymlicka say it is permissible for us to kill animals when it is necessary for survival, though they think all animals have basic rights. They don't explain this in terms of animal rights being particularly overridable, but instead say people struggling to survive aren't in the "circumstances of justice" where rights must govern our decisions. But I very much doubt they think the struggle to survive always puts us outside the "circumstances of justice". They believe starving Eskimos are not in the "circumstances of justice" with respect to seals, but I doubt they'd say Walter White wasn't in the "circumstances of justice" with respect to Brock and Jane. Survival motives give us a prerogative to dispatch animals for self-preservation, and less of a prerogative to dispatch humans for self-preservation -- in fact no prerogative at all.
So--why are animal rights more overridable? What's that really all about? I offer an answer in my book Animalkind, but truth is, I'm still thinking about. I find it a very hard question.