In considering the arguments of legalization opponents, it is important to maintain a sense of historical perspective on the immigration debate, particularly in a nation of immigrants such as the United States.
One hundred years ago, Irish and Italian immigrants who arrived in the United States were widely viewed as members of distinct "races" different from that of the native-born.
David Runsten, Raúl Hinojosa, Kathleen Lee and Richard Mines, The Extent, Pattern, and Contributions of Migrant Labor in the NAFTA Countries: An Overview.