By framing such judgments as pertaining to "internal values", you are already assuming that which you are trying to prove.
As I said, the fact that people have moral disagreements does not in any way entail that morality is intrinsically subjective. The source of such disagreements can easily be attributed to vagueness or indeterminacy in the concepts involved. Both of which can be overcome by elucidation of said concepts.
I myself wouldn't argue for any ontological basis of objective morality, but I do maintain that such a basis can be constructed, and is actively constructed within every discourse by which we attribute meanings to the terms that we are using. Now ethics, as a necessarily normative discipline, is worthless outside the context of human doings. However, within this context, the meanings of our terms are, at least partly, constituted by their use. So the word 'murder', which is used to signify acts of killing that are deemed morally impermissible, already entails within its meaning the fact that murder is morally wrong. Within such a discourse, the statement 'murder is wrong' becomes tautological. Similarly, it is often held that suicide is wrong, however if you frame the same act of taking one's own life as 'martyrdom', it becomes morally permissible or even desirable. The choice of signifier here dictates the scope and context of the situation that's taken into account when forming a moral judgment about it.
It is of course clear that the meanings of such terms can vary, and indeed must vary between different discourses. That follows trivially from the fact that for a discourse, or a system of meaning or a system of signification, to have any signifying value at all, it must enclose itself. The meaning of an element or a term within a discourse is that which differentiates it from every other element within the same discourse. For it to become a system of meaning or a language, the discourse has to form chains of equivalence between its elements. Since the material reality behind all discourses is vast in its things, forms, events, etc. such possible chains of equivalence, and even the notions of what constitute discursive elements, are infinite. And from that, it is the case that every system of signification must limit itself in order not to lose all its signifying power. It must enclose itself and by that presuppose the existence of other possible systems.
Within a given discourse, then, the truth-validity of moral judgments is determined by the validity of the meaningful use of moral terms, as dictated by semantics and syntactic rules of language. There is nothing subjective about this operation.
I am obviously not talking about any metaphysical objectivity here, but ethics as a human endeavor is not necessarily a subjective thing, which is clear from the way that ethical notions are used by us, humans. None of this speaks against moral relativism, which is not to be confused with subjectivity of moral judgments.
The mechanism for such is objective because it physically happens. The variance of the meanings is precisely what I'm talking about, though, and the fact that one thing can mean something different to two different people is in essence subjective in its values.
The value is determined in the individual which makes the value subjective by the very definition of subjective, even though the process by which it occurs is an objective and physical process.
Meanings are also subjective because meaning must be interpreted, so in the case of the word 'murder' you must have a conscious comprehension of the word and its interpretation, which is a subjective event.
I think what you mean is that judgments aren't always necessarily
relative - an example being again the word 'murder' which may universally mean to cause the death of somebody, and doesn't necessarily have to be relative because of that - but relative is not the same as subjective.
Edit:
Or in short form, anything that originates from thought is subjective, in the way that the term subjective is used in philosophy. This should not be confused with the more common meaning of the terms 'subjective' and 'objective' which are often taken to mean whether one is trying to be impartial or personal - this is not what I'm talking about.
Edit edit:
Or to illustrate the difference, if you cause the death of somebody, that is an objective event. If you cause their death and then feel bad about it, you have subjective and objective events going on - their being dead is objective, your having a feeling is objective (it takes some stuff firing off in your brain) but the conscious feeling from your perspective is
subjective since it takes place in your conscious perception and what you feel consciously really has little to do with the dead person. They're dead whether you feel bad or not. If you're not conscious though, then the value judgement does not occur even if you somehow still killed them without being able to think about it. They're objectively dead but the subjective value doesn't arise. So it would also follow that if there's no consciousness anywhere, then there are no values, regardless of what actually happens. This is necessarily, in fact absolutely, subjective.
Edit 3:
Also if you think about it, objective things exist independently of thought, and humans can be unaware of many things that exist, so there could - if ethics are objective - be things that have not been discovered yet, that we don't even have words for, which are already ethically wrong because that is the nature of objectivity.
In fact, since humans can be mistaken about what we know, if ethics are objective then it would be entirely possible that all of our ethics are wrong and we don't know about it.
