This did seem like an odd consequence of Blitzer's argument. For example, it seemed irrelevant that Lincoln was the person who delivered the Gettysburg Address, and that he chose to address the situation in the particular way he did, emphasizing unity over further antagonism. Blitzer's explanation is that some of the situation (needing unity over antagonism, I suppose) still exists, but there are a lot of ways to respond to the urgency of war, and historically a call to unity and peace is not necessarily the natural and dominant narrative. We need to grant Lincoln some agency for making those rhetorical choices which impacted the way the war eventually ended (with the Southerners becoming countrymen again rather then citizens of a deposed state).