Webster's gives us a fairly familiar definition of history
1. The study of past events, particularly in human affairs.
2. The past considered as a whole.
However this really doesn't describe how at least 98% of the population makes use of history. If this were the true description of history, we'd see things like high school history classes studying books and newspapers written during the time when events occurred in the attempt to get a handle on the 'whys' of history. Oddly, we hardly ever see that except on rare occasions at perhaps the dissertation level for graduate students, despite the fact that thanks to Google, such documentation is probably easier to obtain and peruse than at any time in history.
Instead, what we call history is actually the ongoing struggle over who gets to control society's mythic narratives. Control over these narratives is very important, because they are analogous to favorable and unfavorable terrain in the team sport that is the battle for status. One-sided deconstruction of your mythic figures while leaving the opposition's figures fully constructed is strongly to be avoided---in fact I daresay it's practically an act of war. History contains more than enough material to blacken the name of any large group you care to name, especially if you fail to hold opposing groups to the same standards or scrutiny, and if, God forbid, you look at low-surplus societies and those inside them from the prism of a 'holiday from history through fossil fuels' high-surplus society. The left, at least at the leadership level recognizes this...reactionaries and conservatives must as well. Sure, the actual facts and epic messiness of real history can be terribly interesting, but control over the mythic narrative is far more important. One might say it is literally a matter of life and death. Look to the birthrates of Germany and Japan if you need to see what happens to a civilization that allows its mythic narrative to be cast down.