Consequentialism is awesome, except when it’s not. Particularly, the whole idea “inaction to prevent something from happening = action to make it happen minus the cost of action” is a fantastic tool to improve our ethics, make sanity checks of extraordinary claims like “death or disease is good,” and generally be more efficient. However, it’s also a superweapon that should be banned under the Geneva Conventions or something. No one can possibly live up to this standard, and therefore this argument allows you to bulldoze anyone’s position and decisions. It denies any decent person who don’t want to be a murderer choice and the right to be happy, because most of the things that make us happy aren’t precisely the most cost-effective actions to prevent deaths in the world. What’s worse, once people notice that you have a rhetorical bulldozer, they’ll just start ignoring it (don’t try this in the physical world), and you won’t be able to make any arguments.
But what’s even much much worse is that if you succeed, and convince people that they’re literally Voldemort for merely existing, they may as well give up and start doing other Voldemort things too. Unless you really internalized this argument (in which case you’re not reading this, since you sold your PC and donated money to charity – you wouldn’t kill a person to be able to browse Facebook, which means that it’s unethical to not give up facebooking to save a life either), you probably agree that murdering three-four innocent people to buy a new car in a sense of not donating this money to an anti-malaria charity instead isn’t as bad as murdering then in a sense of breaking into their houses, blowing their brains out, and taking the money. But imagine that you succeeded persuading people that it’s basically the same thing. We already know that you can trick people into believing that cheating on their partner isn’t that big of a deal by simply telling them that they’re statistically likely to cheat. If there’s nothing one can do about being a villain, they will redefine evil. People rationalize even potential actions, and for darn sure they would rationalize actual inaction (even I’m doing that right now). Now imagine you convinced them that any rationalization of inaction they came up with also applies to action, and it’s totally OK to shoot people as long as they can escape the criminal justice system. Oops.
OK, what’s about those people whose moral core prevents them from going Voldemort? Maybe they will start helping others so much that the fact they’re suffering doesn’t even matter? No, they won’t. They will drown in depression and self-loathing, but still not become perfectly rational anti-death optimizers BECAUSE THIS STANDARD IS FREAKING IMPOSSIBLE TO LIVE UP TO.
For practical reasons, we probably need an ethical framework that allows us to distinguish bad actions from good actions, without labeling the whole peacefully living population murderers, and without concluding that murder is a-OK thing if you’re not really enthusiastic about it. Oh, and for sure this ethical framework shouldn’t say that it’s OK for Bill Gates to go on a rampant shooting massacre, and still be a nice guy, while a regular Joe is a cold-blooded murderer, since he hadn’t applied every possible effort to maximize the amount of money donated to charity. And we can totally have all these nice things, if we simply accept one irrational axiom: inaction doesn’t equal action.