You can call the social constructs whatever you like and no one is foolish enough to deny their utility. But as you note, they are not claimed to be objective; it is admitted that they are nothing more than (subjective) opinions. In trying to learn what they really are Chris Hitchens and Carl Sagan teach us how to approach invented opinions with Empiricism's perspective: "What can be asserted without evidence can also be dismissed without evidence".
>just an observation
That's really all Hume did with a single paragraph known as Is-Ought. But it has frightful consequences, showing subjective morality to no more than a disposable invention in light of reason and logic. This line of thought from the 1700s that without God morals were made up gave us Surrealism, Dada, modern art, postmodernism, the thought of Max Stirner, Nietzche, Hobbes, Satre, Camus, Marx, Dostoevsky, Bukowski, et al ad nauseum and continues to this day.
>presupposes that your view is correct
If my view is not correct, it should be easy for you to refute Is-Ought. You can't and won't.
Your language is incredibly disingenuous. Another phrasing might be, "useful social constructs." "Delusion" doesn't really make sense as a descriptor of subjective morality since there's no claim that they are objective in the first place. Namely, your description of those who disagree with you presupposes that your view is correct. In particular, it feels like this is just an outright lie:
> The argument isn't to prove that morality is objective or to prove God exists. It is just an observation [...]
If it were "just an observation," your language wouldn't be laced with the presupposition that Moral Realism is the "correct" philosophy.