Do you have a compelling argument that slavery is a crime against humanity?
Perhaps you and GO simply have a different view of what constitutes a crime against humanity.
The UN does not state that slavery is a crime against humanity.
It states:
_____
For the purpose of this Statute, "
crime against humanity" means any of the following acts when committed as part of a widespread or systematic attack directed against any civilian population, with knowledge of the attack:[41]
(a) Murder;
(b) Extermination;
(c) Enslavement;
(d) Deportation or forcible transfer of population;
(e) Imprisonment or other severe deprivation of physical liberty in violation of fundamental rules of international law;
(f) Torture;
(g) Rape, sexual slavery, enforced prostitution, forced pregnancy, enforced sterilization, or any other form of sexual violence of comparable gravity;
(h) Persecution against any identifiable group or collectivity on political, racial, national, ethnic, cultural, religious, gender as defined in paragraph 3, or other grounds that are universally recognized as impermissible under international law, in connection with any act referred to in this paragraph or any crime within the jurisdiction of the Court;
(i) Enforced disappearance of persons;
(j) The crime of apartheid;
(k) Other inhumane acts of a similar character intentionally causing great suffering, or serious injury to body or to mental or physical health;
_____
In other words, the UN only considers enslavement (as opposed to slavery) as a crime against humanity "when committed as part of a widespread or systematic attack directed against any civilian population, with knowledge of the attack".
The UN has even issued the following statement:
That means that the UN believes that slavery is not always a crime against humanity, but only in certain circumstances can it be considered a crime against humanity.
Note, at no point did GO assert that slavery should be legal currently.
True, I think the abuses of slavery far exceed any historic benefits that it provided for conquered peoples and debtors.
Though, I would like to point out that pretty much everyone living today admits that slavery is perfectly acceptable in some contexts.
Prisoners, for example, are, for all intents and purposes, slaves of the State as punishment for their crimes.
I am opposed to the enslavement of offenders in prison as a punishment for crimes.