I think you're rather making their point. Something could be both evil and economically beneficial, and while the statement only mentioned the economy you assum

I think you're rather making their point. Something could be both evil and economically beneficial, and while the statement only mentioned the economy you assume that they have a bad way of looking at the world. We should be able to have a reasoned, intellectual discussion about the economic side of slavery whilst still agreeing it shouldn't be done.