If a moral theory accepted and acted upon by all moral people led to an average decrease in suffering, I’d take that as a sign that it was doing something right. For example, if no one initiated violence against anyone else (except in self defense), I have a hard time imagining how that could create more net suffering though it certainly would create more suffering for the subset of the population who previously used violence to get what they wanted.
If a moral theory accepted and acted upon by all moral people led to an average decrease in suffering, I’d take that as a sign that it was doing something right. For example, if no one initiated violence against anyone else (except in self defense), I have a hard time imagining how that could create more net suffering though it certainly would create more suffering for the subset of the population who previously used violence to get what they wanted.