Louis C.K. has a joke exactly about this called "Of Course, But Maybe":
"Of course, of course slavery is the worst thing that ever happened. Of course it is, every time it’s happened. Black people in America, Jews in Egypt, every time a whole race of people has been enslaved, it’s a terrible, horrible thing, of course, but maybe. Maybe every incredible human achievement in history was done with slaves. Every single thing where you go, “how did they build those pyramids?” They just threw human death and suffering at them until they were finished."