This isn't related to the article, but I wanted to pick at the 'benefits of slavery' question.
I think it's important to acknowledge the 'benefits' of slavery, because it's important to remember who it benefitted and at who's expense. To claim that it benefits no one would be to deny the greed and callousness that spawned these human rights abuses.
Slavery in the past has brought massive advantages and benefits to many people today through the accumulation of intergenerational wealth, at the expense of minorities who are still systematically denied access to this wealth. To claim that these benefits don't exist would be to diminish the scale of issues slavery has brought, and is still bringing, to modern day.