In too many old film comedies there is a stock scene of some drunk arguing with an inanimate object. I think of this scene when I see an editor arguing with dead sources.
Consider Allan Nevins’ book, A Diary of Battle: the Personal Journals of Colonel Charles Wainwright, 1861-1865. Colonel Wainwright was writing a private diary and given the license he might have allowed himself, his entries are remarkably restrained and readable. He could not, of course, anticipate that the legendary Civil War historian and inspiration for Columbia University’s Allan Nevins Chair in history might someday be commenting on his private thoughts.
The subject is managing your sources and our teacher is Dr. Nevins.
Wainwright: “McClellan’s object in coming by the York instead of advancing along the James was to effect his junction; but for a week past the camp has been full of rumors that McDowell did not want to come, and was raising all sorts of difficulties.” (71, Da Capo edition, 1998)
Nevins: “It was not true that Washington’s orders for the disposition of troops had constrained McClellan to advance by the York instead of the James…” [Note: Wainwright mentions no such orders.]
Wainwright: “Every man thinks that he is conferring a favor on the government by being here at all, and commences to pout and hang back so soon as [the] government fails to furnish him with everything he is entitled to. I do not know that this can be remedied in so free a country.”  “As to shooting deserters and cowards, whether men or officers by court martial, that is out of the question, as all such cases have to go to Washington and Mr. Lincoln always pardons them.” 
Nevins: “Wainwright’s readiness to have cowards and deserters shot, and his hostility to press correspondents, shows that he had an imperfect grasp of the conditions under which the American democracy had to wage war.”
Wainwright: “He [Fitz-John Porter] may have been guilty of everything charged against him, or he may have been perfectly innocent, of this I know nothing; his condemnation was a foregone conclusion.” 
Nevins: “Wainwright’s statement is highly unjust to the judges who tried Fitz-John Porter…”
Wainwright: “The news contained in them [New York City newspapers] is little if any more reliable than that in the Washington Chronicle …” 
Nevins: “Despite Wainwright’s disparaging remarks, the Chronicle was widely regarded as the best newspaper in the capital.”
Wainwright: “Her people [Virginia’s] have not only poured out their money and their blood without stint, but from this state have come all the greatest and best men: Lee, Sidney Johnston, and Stonewall Jackson…” 
Nevins: “Wainwright’s belief that Albert Sidney Johnston had been a Virginian was as gross a misconception as his notion that the fighting at Shiloh, Stones River, and Chickamauga was somehow less fierce than at Antietam and Gettysburg.”
This picture is a little one-sided. Sometimes Nevins weighs in with endorsements of comments made by Wainwright.
Nevins: “It was true Hooker was generally piqued…” 
(But Wainwright was recording a letter from a certain Major Reynolds who was piqued and who was a Hooker fan; he did not say that Hooker himself was piqued.)
Nevins: “Wainwright’s animadversions upon Burnside were just and his criticisms are fairly stated.” 
Wainwright: “Very little is said about Burnside, but neither officers nor men have the slightest confidence in him.”  “[Marsena] Patrick tells me that has Burnside consulted him or allowed him to know anything as to what his plans were, he could have explained to him the exact lay of all that land.” 
(Those two remarks represent the entire catalog of animadversions and criticisms. )
Sometimes Nevins just wants to be helpful instead of contentious.
Nevins: “Wainwright’s statement as to Meade’s council of war [before Gettysburg] requires amplification.” 
(Wainwright made no statement of his own about the council, he simply relayed Wadsworth’s account of the meeting.)
Here is more helpfulness.
Wainwright: “[I have] Indistinct visions of some occasion on which I might gallop half a dozen batteries into position at the decisive moment, as General Senarmont did at the battle of Friedland, and so to save the day.” [471-472].
Nevins has footnoted this. He has something important to say.
(Think of the old comedy film. The drunk is now tired of arguing with the lamp and the broom and begins to wax philosophical to no one in particular.)
Nevins: “Wainwright had read French military history.”
A toast to the great Civil War historians and their unruly sources!