You keep using the word "justified". Can I ask who performs the analysis to arrive at this conclusion whether a moral system is justified?

I don't think you understand the nuance of my reasoning. You can ask but you won't receive a fruitful answer. I'm not obligated to actually provide such a calculation or demonstrate that one is even feasible, because I'm not asserting that a particular moral system is justified. Indeed I am asserting that a particular fact, namely the fact of the existence of a particular moral system, does not constitute an argument for the justification of a particular moral system.

If it is a human being, can another human being not possibly perform the same analysis and arrive at a different conclusion?

Speaking generally, not if we suppose that these human beings begin from the same premises and do not make errors in their analyses. Aumann's agreement theorem, which is mathematically proven and therefore true, asserts that "two people acting rationally (in a certain precise sense) and with common knowledge of each other's beliefs cannot agree to disagree" (Wikipedia).

You mean like slavery? Like right to live free? The whole issue that although is now recognised as a universal right, was fought over in the past and divided many parts of the world? Or perhaps, colonialization? Or suffrage? Or every thing that people have gone to war over because they believed they were right and others weren't?

Again, I'm not sure you understand what I'm saying. Please re-read my post, which says that "the overwhelming majority of moral beliefs result from cultural norms and social constructs", which is in agreement with the examples which you have provided, such as "slavery" or "the right to live free".

My argument is that just because morality is in practice often derived from one's surroundings, culture, and social norms does not mean that morality is actually inherently contingent upon environment regardless of how people actually act.

You don't buy a Bentley then claim the Honda is cheaper and complain to the Bentley dealership.

You might not but I don't see how it is logically impossible to do so.

You have the agency to exercise your choice knowing full well the consequences of your action. It's an illogical, irrational decision to make and therefore, the it does diminishes the strength or logical validity of that argument.

This is a generally nonsensical statement. Suppose that one begins with various axioms and assumptions and logically reasons one's way to demonstrate the truth or negation of some proposition P. Now suppose that the aforementioned axioms and assumptions are unrelated to one's personal experiences and that the analytical reasoning used is entirely consistent and valid. Then the truth value of P is completely independent of and unrelated to one's personal experiences. In general, valid moral calculations in any given moral system are independent of one's personal experiences because the axioms that govern moral systems are generally independent of any particular individual's personal experience. Hence there is no reduction or change in the strength or logical validity of the argument.

The argument might appear to you to be less convincing, which is just a failure of your own rationality.

It's not a complaint really, it's an objection to the punishment meted out. It's like saying "this punishment is not valid, I should not be punished." It's a an attempt to weasel out of the punishment the way I see it.

I'm not sure how there is anything wrong with saying "this punishment is invalid, therefore I should not be punished", because the statement "this punishment is invalid" directly implies "this punishment should not be used" which directly implies "this punishment should not be used on all people, which includes me".

I am only arguing for the recognition that the punishment is deserved in the eyes of the law and intervening in that, is an attempt to compromise the sovereignty of the nation executing the punishment.

I'm not entirely clear why you spent so much time and effort arguing here if that's the only point you wanted to make. Honestly, it's a bit silly. Saying that someone foreign disagreeing with a nation is an attempt to compromise the sovereignty of the nation is so trivially obvious that it's almost tautological. It's like saying that someone telling you to not do something is an attempt to compromise your personal sovereignty, which is true and also extremely easy to see because it follows directly from the definition of what it means to tell someone not to do something.

If your intention was to just say that it annoys you when foreigners tell Singapore not to do something, which is like saying that it annoys you when people tell you not to do something you want to do, this is also a pretty trivial and fairly obvious conclusion if you identify strongly with your nation, so I'm not sure what the point of engaging in this protracted argument was. Again, it's true, but it's also so trivial as to be absolutely uninteresting, because wanting to do something almost always means that you don't want to not do it, which means that someone trying to stop you from doing it will be annoying because if they succeed, it means you end up not doing the thing you wanted to do, which is unpleasant for you because we started off with the assumption that you wanted to do that thing. As you can see, this is a pretty simple deduction.

If your intention was just to vent about your emotional feeling of annoyance then that's fine but I'm not sure that getting into arguments with people and subsequently making a lot of nonsensical statements about morality and logical reasoning that betray your lack of rigorous thinking was a very wise idea, just like how it isn't a very wise idea for foreigners to enter Singapore and complain after being punished for committing crimes. Perhaps you might be annoyed by this condescending attitude I'm adopting, but you kind of put yourself in this situation, so should you really be complaining...?