Is there a time knowing the truth is not wise?

As a general rule, the truth is more important to me than most things. But with that said, there is a legitimate question as to the necessity of knowing everything there is to know. For example, most people have heard the stories about George Washington and the Cherry Tree, "Honest Abe" reading his lessons by night and walking miles through the snow to return pennies overcharged to a customer, and so forth. These stories have entered the mythology of Americana and are accepted as truth by many people.
Some historians debate whether these things ever happened. However, many of the same people then argue, "but they have an essential truth in that they accurately portray the character of" Washington or Lincoln, for example. In other words, although the DETAILS are wrong, the RESULT is accurate and therefore it has value.
Maybe. Maybe not. But let's change it up a little. What if you have a positive image of someone and their work as well. An alternate version is presented that destroys the positive view not only of the individual, but also of their work? This raises several questions. Is the character of the individual a key component of their work? Can you separate the two? If the view of the artist changes does that change the perception of the body of work?
This comes up because of a book I am currently reading, Walt Disney: The Dark Prince of Hollywood by Marc Eliot. He goes a long way even in the preface to tear down any possible positive image of Disney. He (and probably rightfully) makes a strong, almost violent attack on previous biographies of Disney as essentially company propaganda. A careless reader might think of Disney as a modern day Teamsters Union from the Hoffa period the way he presents it.
The problem is...he is presenting a compelling argument that Disney was a harsh boss with questionable ethics, a tradition of betrayal, and an angst that surpasses that of almost any other major figure of Americana. To be certain there are portions of his narrative that are clearly extrapolations, other areas where the evidence seems weak and he seems to be writing more with an agenda to destroy a positive image than to realign to more accurate the view of an American giant, and still others that might be outright fabrications. In his own way, his portrait of Disney is no more accurate than those he is trying to dispell.
Is there a need for books such as this? Eliot does have some excellent points. Disney, as any thinking person already knew, was hardly the saint he is typically portrayed as in most stories of his life and work. At the same time, there is something to be said for the value of having some positive role models out there, even if that means hiding some warts.
For example, as much as I despise him, there is something to be said for leaving Kennedy's image as a positive force for our country untouched. Sure, it means leaving unturned stones covering very questionable political practices, deceit, lies, adultery, demonstrated indifference to civil liberties, and so forth...but is there not a certain value to perpetuating the lie that he made progress on civil liberties? It is a little known but easily researched and discovered fact that the much-maligned and despised Johnson was far superior in getting Civil Liberties expanded and protected whereas it was under Kennedy the focus was actually on expanding the role in Vietnam. However, to show that truth to the majority of our citizens could conceivably result in a very damaging disillusionment that could harm them as individuals and the country as a whole.
I do believe there is a certain value to allowing some myths to perpetuate. The beliefs that FDR helped overcome the Depression (the ugly truth being his programs made no discernible dent in unemployment; it was, horrifyingly enough, the advent of war and the buildup of the war industry that brought the country out of the Depression), that Dimaggio was a hard playing, clean living icon, that Hendrix was on to something and his songs have deep meaning, that Disney was who he has traditionally been presented as.
The question is, do you destroy the myth version in pursuit of the truth? Do you hide the truth? Do you ignore it? Or do you mix and match to meet your personal preferences?
If we look hard enough we can find dirt on any and everyone who has ever lived in our countries history. We can point to flaws, inconsistencies, issues, things that bring shame and disgrace...or we can accept that we are looking at an airbrushed history but accept that there is value to that as well. There may not be a right answer but it is at least something to think about.