We all know part of the immigration debate is that the illegals work for below the regular wage rate. What the people who defend illegal immigration are saying is how important this is to the economy. How important it is that they do the work Americans "won't" do (which is misleading at best).
What these supporters are really saying is that it is OK to have sweatshops in the United States. That it is OK to have groups of 10 to 20 people living in substandard conditions. That here in America we need to have people locked up in rooms at sewing machines for 12 to 16 hours a day with no breaks for the restroom or food. They are supporting cargo containers coming in filled with people to be used as indentured labor and forced prostitution.