Howard Zinn and self-defeating pessimism

I am currently reading the ever-popular high school history text-book, "A People's History of the United States". The author, Howard Zinn, looks at American history through the lens of Marxist class-analysis, or class-warfare, as the case may be. So far, the history book has shown me that people have done, in word and deed, horrible things to each other. This is not a new idea to any Christian familiar with the doctrine of original sin, but perhaps it is shocking to secular humanists convinced by Rousseau and blinded by enlightenment confidence.

As interesting and depressing as Zinn's account can be, I cannot help but think something significant is lacking from Zinn's narrative. It is undoubtedly, doubt. Doubt that his narrative might be incomplete. A professor David Bobb of Hillsdale college hits the mark in his review for Claremont:

Zinn answers his own questions, of course, and he presents the Cold War as a struggle between "empires of influence." His interpretation is consistent with his ideology, in which moral and political differences (he berates Democrats almost as much as Republicans) are subsumed in class differences. In his tidy tale of how the rich hate everyone else, Zinn assumes the mantle of chief spokesman for the oppressed. He writes not so much from historical hindsight as from historical omniscience. A good historian will spur questions and prod his readers to investigate his claims. Zinn does neither, but instead makes students fearful, distrusting, and ultimately despondent about the possibility of patriotism. Instead of emboldening them to do noble things out of admiration for the great people and deeds they have studied, his book only serves to embitter them about America.

Has anyone else read this particular history? I think after reading a book like this, it is easy to adopt an attitude where you focus only on evil. A better attitude is one rejoices in what is good and rejects what is bad.