In this chapter, Zinn argues that the Founding Fathers were acting tyranically towards four groups of people. These were African Americans, Native Americans, women, and workers.
In Chapter 4, Zinn does not do much to describe the first three tyrannies. After all, these are well known and he also devotes other chapters to the ways in which these groups were tyrannized. Instead, Zinn uses the latter parts of Chapter 4 to argue that the Founders, and John Locke who inspired them, espoused egalitarian ideas but only gave them lip service. He argues that they only meant that white men of a certain level of wealth should be equal to one another and should be able to be part of the dominant class of the society. He ends the chapter by pointing out that the rich were allowed to buy substitutes when all men were ordered to turn out for a "military draft" in Boston. This, he says, led to rioting and symbolizes the ways in which the rich were tyrannizing the workers.