I think that the primary argument that comes forth out of "Drawing the Color Line" is the establishment of a firm social and political demarcation between people of color and the ruling majority society. Africans who came to America through slavery and their African- American descendants were subjected to the harshest of conditions in terms of treatment and physical labor. At the same time, Zinn makes the point that White society did as much as possible to keep people of color in their subjugated place at the bottom rung of the social hierarchy. Zinn suggests that there was a clear correlation between the rapid influx of slavery in North America ("10 to 15 million" imported by 1800) and the need to institute controls upon the people who were imported in as many domains as possible. Zinn shows that the social desire to keep control was a part of the culture of slavery so prevalent in America at the time.
For Zinn, the establishment of "an intricate and powerful system of control" was reflective of the need to continue generating profit from the institution of slavery. These become the primary points of the arguments generated in the second chapter, reflective of the idea that control and consolidated expressions of power lay at the heart of the nation's formation.