its same concept with Alcohol and many other things humans do
Alcohol was first labelled as Najasa smth dirty like Pee
later on it was completely prohibited
when someone tells you to free the slaves
like i said that was at a time it was quite common but u dont seem to understand the difference of time and even so they always told people firstly to treat them humanely secondly to free them if they can
Islam is there for every period of time
so the regulations are based on time
to stop everything prohibited and harmful at most
where slavery was common to the point u cant completely ban it
so u have to have a regulation to stop it slowly until its gone
u didnt provide any source for that
400 years of slavery where slaves where slowlyturning around?
and most slaves have integrated into the socitey?
and lets say they did ban it
why until this day theres many people that still hold slaves?
or you gonna turn a blind eye for that?
when the richest does it its fine?
the irony is the mahdi takes after the prophets name