What was an argument made by progressives agains child labor?

Answer 1

it hurt society for the children to not attend school.

Answer 2

Many children today are actively involved in responsibilities that aid the earning and living standards of the family some families live in jungles and the children are learning to make a living in this way. Yet others work with their families in what is described as sweatshop conditions to make cheap clothing and other articles right in our midst in the developed countries. These children go to school and will probably prosper in later life because they understand what work is.

Then you have the poor little blighters that are virtual slaves usually in under developed countries that don't receive an education and work under conditions that can often lead to chronic illness in them. The goods that they produce are regularly seen on supermarket shelves and they should not be there. However the ethics of the self-regulating market has no conscience and only looks toward the extra dollar.

Child slavery plays a big part in keeping the price of diamonds down so the practice should be kept in mind by all those that give a diamond ring as a symbol of their devotion.