The Best of All Possible Worlds?: Time Travel, Part III

“The moving hand once having writ moves on. Nor all thy piety nor wit can lure it back to cancel half a line.”
--Omar Khayyám
 When your characters have the ability to rewrite the past as we know, it simultaneously opens up fantastic opportunities for innovative explorations of history, and opportunities for re-entrenching the dominant narrative, with all the attending unpleasant implications. As a fan of alternate history-- particularly that which makes us look hard at how we arrived at our present-- I'd definitely encourage writers to write stories where characters can alter events as they occurred in 'our' timeline.  At the same time, whenever an author makes an executive decision about 'point of divergence' in their alternate history timeline, they will have to decide how to shape the resulting alteration of events, and, more importantly, decide whether the narrative will treat these outcomes as positive, negative, or ambiguous. 
The more subtle trap is that of hindsight bias, in which we assume that historical events-- particularly bad ones-- were the only possible outcome, and perhaps that the events were inevitable on a larger, less specific scale. Thus we have stories of characters attempting and failing to prevent the great and small tragedies of history and failing. This in and of itself is not a problem if handled with sensitivity. However, if the story returns to support the implied narrative that the tragic event was inevitable in the grand scheme of things, thus quietly absolving the very real perpetrators of responsibility, you've shaped this into a core message of your narrative (as usual, we can blame Walter Scott, father of historical fiction and lead henchmen of the colonialism apologists, for kick-starting this one). This gets exponentially worse and more prominent if you prop up the 'inevitability' theory by dragging out well-worn arguments which boil down to the recipients of the violence or general horribleness having had it coming in some way. I know it's an easy trap to fall into, but it can be avoided with some careful examination of the story.