> Your syllogism equivocates on the concept "observation" and does not follow.

I was going more for an analogy than an equality. I also did not mean to imply that the relevant moral observations are how one derives moral principles. The relevant observations are the questions: "I perceive situation X in reality. Is injustice present? Who has been aggrieved, and is there an aggressor?"

These are clearly observer dependent.

> Moral discussions are not a "game" since lives and, ultimately, civilization hangs in the balance

I vacillated on using the word game. The game isn't morality, but pondering what morality is. If I had called it a thought exercise I think it would have had slightly better connotations. I call processes of cognition games perhaps too often.

With respect to objectivity: Not even scientists attempt to achieve objectivity. They merely attempt to reach consensus. It can be a bitter and contentious process in even the most quantified sciences. For example, the disagreement over whether tetraquarks exist [1]. Objectivity is a naive concept. You cannot prove that your perception of objectivity is, well, objective. Objectivity is at best a useful fiction. It's actually a very useful fiction! But it can fail because one's understanding of objectivity cannot verify that it is objective.

I think you can imagine a kind of person who claims that others lack objectivity when they are disagreed with. They exist everywhere. There's a named logical fallacy for this kind of behavior. Demanding one's morality be objective does not make one's morality objective, but it means that every moral judgment one makes is now self-judged to be objective. The moral framework can be internally consistent but inconsistent in its reification into material judgments and actions.

> Moreover, your position assumes two things that the radical Islamists do not share; the value of a human life (in the here-and-now not some fantasy world) and that reason, not guns, are the means for resolving disagreements among civilized men.

Ok, so we're talking about "radical Islamists" now, so I'll assume you mean Daesh because the vague "radical Islam" is just a snarl phrase. Is Saudi Arabia an example of radical Islam? They're an ally to the United States. Notice how the countries that claim "reason, not guns, are the means for resolving disagreements" quite willingly and openly and readily act in direct contradiction of those ideals. There is a discrepancy between what people say morality is and what they do. Everyone loves their morality when it permits them to dominate others and shape the world the way they see fit. Everyone's morality permits them to commit atrocities.

I am a moral realist. I merely make the claim that a person should not believe they have a direct apprehension of moral truth because such a belief compromises the ability to apprehend moral truth. Therefore I demand of a person's moral framework that it be oriented towards analyzing and understanding differences between people's moral judgments. If I assume I am capable of understanding moral reality and meet someone who disagrees with me, I can either conclude they are incapable of the same understanding or the disagreement stems from different vantage points.

Believing two moral individuals can come up with different moral judgments in the same situation is the only sensible starting point towards reconciling conflicts. Understanding why moral people can come to different moral conclusions is the fundamental mechanism of justice. Otherwise violently asserting one's moral truth is the only mechanism.

> How do you deal with someone who not only doesn't share your moral "sentiments" but wants to actually kill you? Is there some basis to compromise in this case? Why do we shoot lions and bears instead of trying to reason with them? Is it moral for you to kill a fly in your house? What if I disagree and claim all life is sacred and you have a moral duty to leave the bugs alone and I am willing to use my guns to protect them from you? On what grounds could you possible oppose someone like that if you really believe morality is relative (i.e. subjective)?

I think you're missing the point. Just because science is supposed to be done via reproducing experiments and corroborating results between different scientists doesn't mean that science is paralyzed by the existence of a person who believes in crank theories and cannot properly run experiments and thus cannot effectively communicate their scientific activities to other scientists. Likewise my morality isn't paralyzed by hypothetical bug-zealots who act maximally unreasonably. If you believe the world is filled to the brim with brutish idiots with whom you cannot possibly communicate moral sentiments, well, I'll have you know there are plenty of them that feel exactly the same about you. How are you different? Your internal moral framework is no proof to me that you have a correct moral understanding of anything.

Here's a better example: You come across two kids at a playground. One sticks their tongue out at the other who then throws a punch and starts a fight.

30 seconds earlier, I saw the kid sticking their tongue out shove that other kid to the ground. Then I saw exactly what you saw.

I'm pretty sure our moral judgments are going to be different.

The real world is vastly more complicated than this contrived example. When you come into moral conflict with other people you can either assume they're a bunch of illogical, fact-spurning hate machines like the top-level comment in this thread[2], or you can believe that your difference in values and moral judgment of a situation arise from a difference in context which can be reconciled through communication and deliberation. If humans can't practically know everything in order to come to an absolute moral judgment, human morality is functionally observer dependent. That doesn't mean there isn't a moral reality that doesn't care about the vagaries of human perception and social context, it's just not practically accessible.

[1] https://www.quantamagazine.org/20140827-quark-quartet-fuels-...
[2] https://en.wikipedia.org/wiki/Illusion_of_asymmetric_insight