I'm guessing you're being downvoted for comparing software to slavery. Generally speaking, the modern society seems to have forgotten that the world isn't binary - you can make comparisons and have similarities that are far apart on the spectrum so aren't equalities, but can still find informative meaning.

But to your point, this exact argument was used by top southern politicians to justify slavery! It was the freedom of the slave owner, their right to own property, that justified slavery. James Hammond famously made this argument to congress shortly before the Civil War broke out. If this is interesting to you, Eric Larson just released a great book called "The Demon of Unrest" that covers this.

The point is understood, but it is a problem with copyright laws, and not only with the license.

This is why I had suggested before, that if you cannot just abolish copyright laws, then to make the license which will allow freedom except that it cannot further restrict anyone by further copyright. No attribution is required, no notices of changes are required, etc; the only requirement is that any further restrictions you claim on your version will be invalid. This is therefore effectively similar than as though you did abolish copyright laws, but only this program. (However, for practical purposes, I had allowed to (optionally) relicense by GNU GPL3 and GNU AGPL3, although only if you are able to follow the terms of those licenses (e.g. having the source codes available, knowing who wrote the original code, etc).)

Who are the slaves in this analogy?

I would say that the users are the slaves. Without GPL software, we could end up in situations where hardware vendors stop shipping software updates, so we are slaves to capitalism by having to buy things we shouldn't need to buy.

This goes hand in hand with right to repair in my opinion.

I don’t think you’re pro-slavery, but I do think you picked a metaphor not for the light it sheds on the issue, but the heat—and then preemptively dismissed a strawman objection to it instead of, say, improving your own communication.

The parenthesis was an edit that I put after receiving downvotes.

I think the comparison is correct, in that who claims copyleft licenses are less free only considers their own freedom, not that of the society as a whole.

And it seemed a good example since most people will have heard of that, if not studied it in school at the very least.