They had just been handed the most severe defeat of the war in a series of defeats in 1862. Moral was low and Lincoln was "glossing" over the facts in order to say to the troop "You are brave, and couragious, and the losses were not that bad as they might seem" in order to rebuild moral and change the commanding officer from Burnside to "Fighting Joe" Hooker without totally destroying the functionality of the army, who could look within their own ranks and see the actual damage done.