I cant speak for all historians or all instances, but I can speak specifically to one conflict, the American Revolution.

For years the English were presented as the Bad Guy (and in many ways still are), which is definitely in part due to the American vantage point but is often reinforced with real historic events like the burning of US homes and towns, Tarelton's troops' slaughter of surrendering soldiers, or simply the "imposition of will" upon the colonists who were just poor old farmers that wanted some liberty.

What we leave out is the brutal acts of violence committed against loyalists and their homes, the Confiscation Acts allowing their property to be seized and them exiled without due process of law (imposition of will, much?), the slaughtering of surrendering English soldiers while shouting "Tarleton's quarters!" as revenge instead of justice, or the actual fiduciary responsibility to contribute in response to the money spent to secure the colonies by the mother country. We destroyed ~350 cases of tea in one protest (destuction of property today, even for a "good" cause, isn't much differently viewed than it would have been then - disruptive and extreme). Even "lynching" as a term started with Charles Lynch and his court in VA denying due process to suspected loyalists in the late 1770s and early '80s. The downside of all this is a lack of history about those actions and about loyalists in the years following the revolution and for some time after - presumably nobody in America cared enough to write it down in the story of America.

This wasn't right vs wrong - as much as we may want to see that. There were some great things that came from our foundation, spreading liberty to corners of the globe with our brave stance establishing a republic based on consent of the governed. It also permitted slavery to exist theoretically longer than England would have permitted otherwise and led perceivably to worse treatment of native nations. So there were things we define as good and things we define as bad (but really they were just actions in time - our perception assigns the label).

It's very important for everyone to remember in most conflicts there aren't good or bad sides, but leaders doing what they feel is best for them and theirs. Everyone is the hero in their own story and events are just events. It's up to we historians to view and contextualize those people and events, and their benefits or remifications, accordingly.