Imagine a purely hypothetical situation where objective morality allows something that is normally considered wrong, like robbing a bank. This is not because of special circumstances such as saving a life or being forced. The idea is that objective morality itself simply says the act is allowed.
The question is whether objective morality still makes sense in this kind of case.
If morality is objective, then its rules are supposed to be independent of personal opinions and applied consistently. That does not mean the rules can never be complex, but it does mean that any exception has to be based on a clear principle, not on an arbitrary decision. If an exception exists, it must be part of the moral structure itself.
This leads to a further question. If objective morality allows an action that we usually see as wrong, does that mean the action stops being wrong altogether, or does it remain wrong but become less serious? Either answer is possible, but whichever is chosen must be explained in a principled way. Otherwise, the idea of objective morality becomes unclear.
The issue here is not whether morality must be strictly yes-or-no or whether it can involve degrees of seriousness. The issue is whether adding exceptions forces objective morality to become more complicated than necessary just to avoid contradiction.
Logically, any system of objective morality must be internally consistent. A hypothetical exception cannot simply cancel a rule without explanation. It must fit into the system in a way that makes sense.
At the same time, these hypotheticals matter for how people think about morality. If someone is told that objective morality allows an action they see as dishonest or unjust, they face a choice. They must either change their understanding of honesty and justice or reject the claim that the action is morally allowed. This does not disprove objective morality, but it does create tension between moral theory and moral judgment.
So the real question is not whether objective morality is logically possible, but whether it can stay both consistent and meaningful for human decision-making when it allows actions that strongly conflict with our moral intuitions.
APPENDIX
There is no evidence or proof against the view that morality is binary, just a simple yes or no, with no grades of rightness or wrongness. We are not talking about that at all. If morality is objective it would endorse in the name of honesty, a minimal, least speculative methodology. Minimalism means no more structure than is strictly required, even if what is required turns out to be very complicated.