Mauritania and Sudan still retain their old slavery systems, though in a covert fashion. The mere fact that such slavery system is retained in a covert fashion evidences the fact that the general attitude and aptitude regarding slavery has tremendously altered over time. This is precisely what I had implied in my referred statement. Trust me the system is thoroughly evil. I would not question the validity of your statement, as I am not directly exposed to the system, yet I would only like to mention that not all thoroughly evil systems should be termed as slavery .
Slavery is a distinct institute with generally recognizable features.
Nevertheless, I would not differ with the idea that all such human activities, which, directly or indirectly, result in the exploitation of other human beings should be taken as an abominable mark on the conscience of the whole human race. I agree with you. It was only at a very later stage that mankind reached a stage where the collectivity could plan and implement programs for the macro-level eradication of the vice. Till such time, individuals could naturally be prompted against the vice, but no collective action could have been taken for this purpose, and this, in my opinion, is precisely what Islam did. This, in fact, is the point of disagreement between us.