Is it true that there is no absolute morality?

[Nonpareil]

Okay, so a system can be both objective and subjective, but not a value system.

No, benny. I was pointing out that you were going off track, not backpedaling. Brains are objective, inasmuch as they can be stated to have objective existence. The value judgments that they make are subjective. Et cetera. It is still not possible for a thing to be both A and not-A.

Let's consider the possibility that the brain makes the value system.

In which case said value system is subjective.

We experience that process of value formation subjectively, but the brain functions objectively, i.e. by the rules of physics.

That is not what "objective" means. "Objective" means "true from every frame of reference". That the brain is functioning is objectively true; the ideas that it comes up with may be only subjectively true.

Unless you want to demonstrate things like free will, then we're left with all moral systems being both subjective and objective.

No.

1.  Things in reality ARE both "A" and "not A" at the same time.  That's the essence of QM superposition.

There is an equivalent to Godwin's Law which applies to quantum mechanics.

If you try to bring it up in a discussion without at least three doctorates in related fields, you have automatically lost.