The person above wasn't making a reasoned persuasive argument, they were making a moral assertion. The purpose wasn't to insult someone nor to convince them. It was just an expression of moral outrage.

That's precisely what I pointed out.

Yes, but your comment reads as if you were giving feedback. Implication is that the intent was or should be persuasion, and you saying it's failing at that. Anyway, I don't think "I condemn you for X" is an insult of the normal sort where it's ad hominem, even though it would be better and less ad hominem as "I condemn the idea" (as opposed to the person).

Thank you. This is exactly correct. I was fully aware that I wasn't making a persuasive argument and it wasn't intended to be one. I wanted to emphasise and reiterate what I believe is a widely held moral norm.

The commenter I replied to seemed to unaware how far they had strayed beyond reasonable ethical statements. I don't think I could persuade them to change their position but I couldn't let that go unchallenged. Norms change one person at a time and speaking out is important.

cool

What, exactly, is the persuasive counterargument for basic morality? Why isn't morality axiomatic?

Let's put it this way - the argument above would also apply to saying that a private citizen who catches a thief stealing their catalytic convertor can torture them slowly and painfully for weeks without actually killing them. You owe them no moral consideration, it's a deterrent, etc. Do you need someone to make a persuasive argument against the merits of that to realize that it's abhorrent?

If morality were axiomatic, then worldwide we would have a collective shared understanding of what is right or wrong, immutable over time. That’s clearly not the case.

maybe not in every detail, but are the broad strokes really so varried?

Certainly morality is a shared part of us all, it was evolved to create ingroup cohesion and resist outgroups in humans, so there are a lot of commonalities like reciprocity, justice, etc.

It’s the divvying up of ingroup and out group that tend to create disagreements in morality. I.e. we understand forgiveness, but we disagree who is worthy. We understand justice but we disagree who deserves punishment or why.

That tends to make a pretty big difference in results and conclusions.

Yes.