We have to simply ignore the bit about slaves having no freedom…
(If you read this comment and think I am pro-slavery, you are not apt at human communication and should take steps to improve)
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.
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).)
This goes hand in hand with right to repair in my opinion.
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.
I license all my stuff with permissive licenses because (in my opinion) they are more free than the GPL and such licenses. I don't have any massive for-profit company pushing me to do so. Mr. Kling is also not a massive for-profit company, he's just a guy making the software he wants to make. Your argument is in very bad faith.
Permissive licenses doesn't grants you less freedom than GPL, infact it grants you more because the user also has the freedom to modify source code without being enforced to make it public.
Companies copying the codebase to their propietary ones won't automatically strip right of users, licenses don't work like that, the original codebase will still be fine. Whether said companies will contribute back is irrelevant.