U.S. honored Civil War enemies by naming army bases after them. Why?

In this photo provided by the Library of Congress, Braxton Bragg, an officer of the Confederate Army, shown sometime between 1860 and 1870, location unknown. (AP Photo/Library of Congress)

How did the United States come to have nearly a dozen military installations named not after its heroes but after its enemies — men who led a war against the country and killed tens of thousands of people in defense of the indefensible institution of slavery?