Theistic morality

[Purple Rabbit]

So as I understand you correctly the "That doesn't mean that there isn't a rationally based moral code which would have been true in the past, regardless of what people believed" refers to your perception of a moral code that you think should apply at all times and in all places. But, dear friend, that is your subjective opinion. It is an OUGHT, a prescription, not a FACT. As such it has no more value than any other opinion on the matter. Also I think it is silly to, as you propose, judge historical events on this basis. You can say that according to your moral standards now you dissaprove of certain historic facts in the past, but as a prescription for the past it has no meaning and it will not change a thing about those historic facts.

Of course my believing that something in the past was wrong won't change it. Why is it therefore silly to make moral judgements about them, given that my intention is not to alter history like some crazed mad scientist (though I might if that were possible)?

The only sensible reason to assess morals in a historic context would be to draw conclusions for the future from not to judge the past.

Your assertion that my moral views are no more than opinion entail that you subscribe to a form of moral subjectivism,...

I subscribe to a form of moral relativism.

...which would mean that you couldn't consistently condemn any action.

I disagree. I could condemn actions consistently from a framework of my choice or from a framework that is shared in a broad sense. This is precisely what is the process that led to the Declaration on Human Rights. Your alternative implicitly is a claim on absolute moral truth. Because your frame of reference is necessarily absolute if it is not subjective. So your claim that you can condemn actions consistently and objectively is a totally unsubstantiated claim of the absolute.

Besides, moral subjectivism is very controversial within the philosophy of ethics, and most contemporary philosophers reject it.

That's the fallacy known as the argument from authority. Philosophers would be out of work if they thought it was an argument at all.

Even if it is just an opinion, that doesn't mean that my moral system is no more defensible than any other, assuming that we have already accepted the validity of some kind of moral judgement.

First part, OK that's what I call relative moral. Second part, not OK, it is not necessary to a priori accept some morals to define a relative moral framework.

I can agree with that and, based on what I have seen you writing here, we actually might share pretty much of the moral values. But the formulation of opinion won't make it fact. The only thing that might help is sharing it in the broadest possible way, the result will be something like the Declaration On Human Rights and that is available online.

Again, if you think morality is mere opinion, then the Declaration on Human Rights is no different from a lengthy and articulate text on the merits of strawberry ice-cream.

It definitely is not mere opinion. It has a noticeable effect on the world we live in because it is broadly shared opinion.