Why does the author believe that the contemporary view of Abraham Lincoln should be re-evaluated as noted in the collection, The Vintage Mencken?

Mencken questions the contemporary historical view of Lincoln as a great president and near-saintly figure. Mencken claims there are several realities in Lincoln's biography—such as his issuing the Emancipation Proclamation only when it was politically valuable and not before—that beg for Lincoln to be re-evaluated with a more objective eye.