Have begun Clash of Extremes and am quite impressed. The book opens with a broad rejection of James M. McPherson's work in the inevitability-of-war school. At the same time, it does not take an exclusively economic view of events nor does it take any heed of the world made by Lew Rockwell and Thomas DiLorenzo.
Tom Rowland referred to McPherson and Co. as "Unionists," representatives of (I would say ardent partisans for) a particular historiography. This grouping of like-minded friends into a school was a signal contribution of George B. McClellan and Civil War History. My own "Centennialist" is a little more specific in referring to Unionists united by connection to American Heritage and closely associated with the commercial success of Centennial-era historiography (which McPherson repackaged in Battle Cry).
In Clash of Extremes, Marc Egnal refers to McPherson and ilk as "idealists" representing an idealist school of history. This is broader than "Unionist" but still very useful in accurately depicting the kind of historian that takes a normative interest in past events.
I might argue that idealists can't do history at all, but that's for a future post. Back to Egnal for now.