There has always been a grand scale distortion and manipulation of history not only by individuals but by countries. Most of the time it is to conceal the truth about their past and other times to suppress their population and others to question past deeds of their countries. You can say that since history is in the past and is written by historian who may or may not be on the payroll of the government or maybe from the majority of that country, there is always a bias in mentioning different episodes in history which may not be flattering or depict the current regime in not so favorable conditions. It has been going on throughout history and is not a recent phenomenon.
There are many instances like the Armenian killings in the early twentieth century, the rape of Nanking by the Japanese Imperial Army, the systematic near extermination of Jewish population by the Nazis, the creation of Bangladesh from Present Pakistan and the resulting atrocities on both sides, the killings in Cambodia and Laos, in Rwanda and Congo and now in Syria and so many other places. Now if you see the books of those countries very few of them will mention correctly what happened since no body was there to witness it. It is all about he said, she said. Most of it is done to conceal the fact that the governments don’t want to acknowledge that their previous generations were complacent in the unholy deeds and at other times, there are some ultra nationalists in their population who genuinely believe that it was done out of necessity or not done at all. Anyway it is really very dangerous when you suppress facts since the so called future generation of victims never gets justice.