Subjectivism regarding morals is a brute fact. Call it a “cop out” if you like, simply because the facts end an otherwise “fun” debate (read: willfully blind circle jerk).
While I agree with you more than disagree with you on your view of ethics (i am a moral nihilist / amoral / noncognative / refuse normatives/ etc)), it’ defeats the purpose of a thread like this to go “meta” on the topic. It’s best just to enter “meta” threads about morality than more specific focuses,as it will end up confusing too much / straying off topic.
In this case, the OP was probably already under the assumption of morals or an existing liberarian framwork of morality for example
What do you mean by “real slavery”?
You really have no clue what he was getting at? I did. In the traditions of slavery outside of leftism (wage slavery, and other stupid categories) under what customs were cultures and law calling people slaves? Get that general picture in your head, and use that.