Either "historical revisionism" (a legitimate reinterpretation of orthodox historical views) or an illegitimate distortion of the historical record (a.k.a. negationism).
There are two major meanings to the term "revisionism" in history. Which of these is used will depend on the author's intent.
(1) "In historiography, historical revisionism is the reinterpretation of orthodox views on evidence, motivations, and decision-making processes surrounding a historical event." Source: Wikipedia
(2) "... the illegitimate distortion of the historical record such that certain events appear in a more or less favorable light [...] which — if it constitutes the denial of historical crimes — is also sometimes called negationism." Source: Wikipedia