If evil is a power and/or psychologically treated as a power then we might be tempted to try and use it up - to get rid of it or to at least reduce it.
Let us make a hypothetical assumption. It is that people have a finite amount of evil energy. Doing a bad act genuinely reduces the remaining evil. If not expended, that evil will later - maybe even cause greater harm.
Many people claim that facing the evil and doing it freed them to be better persons. Many suspect that is how evil can work but will not admit it. Many take a moderate view that giving into an evil may lead you to doing another evil. They may assert that the new evil would be a worse one if you repressed.
So should John be praised for committing murder for he said that he only or mainly did it to expend the evil? What if he argues that the evil, if repressed, would get stronger and worse?
What would those who think objective morality exists say? They have different answers.
1. Consequentialist objective morality (results-based)
If morality is objectively grounded only in outcomes, then yes — murdering could be morally justified in principle.
If murdering causes harm H and not murdering causes harm H+10 later, then the objectively right act is murdering. This is basically act utilitarianism, and it bites this bullet happily. No contradiction. BUT: even here, the justification is instrumental, not expressive. Stealing isn’t good because it “lets evil out,” it’s good despite being evil because it minimizes total damage.
2. Deontological objective morality (rule / rights-based)
Here the answer is simply no - the murder is still wrong and forbidden. Why? Because these systems hold that some actions are wrong regardless of downstream benefits. John may not violate someone’s rights as a means to moral hygiene. Even if evil is finite, using another person as a moral sink is impermissible. The wrongness comes from what the act is, not what it prevents.
Think of Kant who would say, “You don’t get to punch one innocent person because it stops you from punching five later.” The moral law isn’t a pressure valve.
3. Virtue ethics (character-based)
Also mostly no, but for a different reason. Even if evil is expended, the act still shapes character, corrupts practical wisdom and normalizes vice as a coping strategy. So you might end with less total evil energy but a worse moral agent, which is a failure by this framework.
4. The hidden problem in the hypothetical
Even granting everything in it, there’s a quiet instability there. If people know evil can be safely expended, then moral self-control loses its point. It incentives shift toward scheduled wrongdoing. Responsibility gets reframed as maintenance. At that point, morality collapses into moral accounting, not moral judgment. Objective morality stops being about right and wrong and becomes about resource management. That’s not a contradiction — but it is a radically different thing than what people usually mean by morality. It can help those who argue that objective morality might not be what we want it to be.
If evil were quantifiable, finite and reliably reducible by wrongdoing, then some objective moral systems would allow murder and theft etc in rare cases. But it wouldn’t be because those acts are healthy or good. So the hypothetical does work — but only by smuggling in a very specific kind of morality and quietly redefining what moral responsibility is.