The parent comment basically says "copyright is not a physical good or law, therefore we may disregard it".
As if the same couldn't be said for any verbal agreement, sexual consent, property rights, whatever.
They ought to be arguing why this _particular_ verbal agreement/social contract is not worth enforcing or practicing, rather than dismissing the entire category.
The map: debt.
The territory: guys who come to your house and kick you out for not paying your debt.
And if you don't believe social constructs to be real, then I am confused as to why in your original comment "money" is given as something which is real. I think one could reasonably say that all social constructs are "imaginary" (whether that is useful is another question, but I would say it is not), but I find it more difficult once you engage in line-drawing within social constructs, especially so when you don't specifically articulate a boundary.
You are redefining the word "real". You know this. Some people get a delight from redefining words and seeing the reaction. It is rather tiresome; it doesn't help constructive debate. What have we accomplished here? Have you convinced anyone?
Feel free to disagree with a particular social norm or law and present your thinking.
If you want to get into epistemology, please do. But we have to find a shared language that makes sense.
Debt is not a real thing. It's a fiction. Subverting contract law is not like subverting the laws of physics. Simply don't pay your bills! What happens when you subvert contract law is some guys with guns, in either an overt way or a subtle one, force a trade of your imaginary resource (money) for the real resource (labor), through a contract.
It's a bit of clever misdirection to declare yourself "in debt" or "debt free." Money is made up! It's fiction! It is whatever we want it to be!