There's something I call "the experience calcluation problem". I expect this would be an extremely common objection to many of my beliefs if they were more widespread. That's why I'm making this article to refute them in advance. The experience calculation problem is:
There are many areas in morality where we need to compare the magnitude of positive or negative experiences, for example to determine the magnitude of a debt or the amount of retribution that can be exacted. What if someone punches me in the face and I claim they owe me $10 in return but they claim the harm was only equivalent to stealing $5? How do we determine how much it's worth?
The Protagonist answer is, "the magnitude of a grievance is the magnitude of the suffering caused, and this determination must be made by each individual".
And a challenge to this I sometimes receive is, "that wouldn't work because there's no way to prove from the outside how much a person suffered, and if each individual judges for themselves and thinks themselves right then they'll engage in conflict. Your ideology is broke because it has no dispute resolution system".
But the argument about how much is owed doesn't depend on how easy it is to agree on in practice. That is an appeal to consequences. After all, the reason it's hard to agree on isn't that it's subjective but that we all lack full access to each other's experiences and can be dishonest.
With that refuted, the next thing I need to point out is that everyone else's moral system has these problems too. From your typical statist non-philosopher to an absurd absolutist like Nullus Maximus, everyone has to deal with this. If you believe that punishment should be proportional to the crime, your ideology has to deal with the problem in the above scenario.
The answer given by statists is generally that legal authority will and should decide what degree of punishment or restitution is appropriate. But in no way can this be anything other than an appeal to either consequences or authority, because what's moral doesn't depend on what the judge or jury decides. In fact, as someone who directly experienced neither person's side and most likely does even know either person, such people are not even in an especially good position to judge, and the only reason this ideology seems to "solve" the problem is that everyone is forced to go along with their decision regardless of how cruel it is. The problem of someone making a bad judgement is not solved, it is legitimized and codified as law.
Actually, the statist answer could be understood as a consequentialist argument, but that doesn't seem to be how statists mean it. If their argument were only that the use of legal authority to solve this problem is an evil justified but not purified by its ends, it wouldn't be as appealing as they seem to find it. It would also only be an argument against stepping outside the law in situations where vigilantism would indeed be counterproductive in the long-term.
Nullus Maximus has touched on the problem a couple times but never said anything more detailed than "people will work it out". So to be fair I'm not accusing Nullus Maximus of believing a fallacious answer to this problem, but as far as I know he has never explained the correct answer.
Yet another problem with attempts to answer this problem differently than I do is that even if you could have a more "objective" criterion, it still wouldn't solve the problem unless you had all the relevant facts. For example, if you used a criterion based on physical forces, that would only help if you were there to measure the punch when it happened.