How we label certain social, political, or cultural phenomena matters a great deal; labeling gives meaning and understanding, and it also gives power. We can see this very clearly in my area of expertise—terrorism—where almost all state definitions of the subject do not consider any terroristic acts committed by states as formal acts of terrorism. The state’s label of what constitutes terrorism carries a great deal of ideological baggage, asserting the state’s sovereignty and its monopolization on the legitimate use of political violence. Genocide studies face a dilemma similar to that of terrorism studies. The term “genocide,” surprisingly, can often be too restrictive. No one really knows what genocide means, which explains the popular use by government officials of the less provocative term “acts of genocide” when dealing with instances of mass violence. Christian Gerlach has argued that the contemporary use of the term “genocide” carries too much emphasis on the political—in other words, genocide occurs primarily from certain structures or ideologies within a state’s institutions. For example, the Holocaust took place because of the German state’s racist policies and its propaganda that rationalized to the German people mass violence against Jews. Genocide is therefore seen as something distinctly political, led foremost by the state. Most importantly, the use of the term genocide, much like that of terrorism, is to cast blame and moral condemnation. Gerlach ditches the genocide label for this reason in favor of the term “incredibly violent societies.” In doing so, he’s able to more accurately account for many other groups, like non-state actors, that affect the turn toward or against genocide.
In other words, I think using the term genocide is more an issue of political and social power dynamics rather than presentism. While I'm sure this is obvious, people can only label things after they've experienced them. An analogy might help clarify why I don’t think it’s an issue of presentism: Hippocrates coined the term “cancer” around 400 BCE. Before the term was coined, however, people still suffered from a disease that occurs due to the over-production of white blood cells that in many cases leads to death. Just because the term “cancer” had not been coined yet didn't mean there was no cancer before that time. Applying the word “genocide” to events that occurred before the term was coined works much the same way. Ben Kiernan, a historian of genocide, makes a similar argument. Sticking to a clear and consistent definition of genocide gets at the essence of the subject—why it arises, how it is carried out, and how societies respond to it. Many historians argue that the genocides of the 20th century are much different than those of previous centuries. A consistent definition of genocide applied throughout all of history allows historians to trace the continuities between these two eras of genocide, and to ultimately see both how the phenomena has changed but also what is constant throughout time.
I'm not sure if this is entirely clear since I typed it up pretty quick. Ultimately, I think that there are definitely benefits to applying the word genocide to instances of mass violence, even if the term had yet to be coined in the period being analyzed. But we also need to recognize that the term genocide carries with it a great deal of ideological baggage and that the term can easily slip into dangerous normativism that is meant primarily to cast blame rather than give clarity.
Oh lookey here we got an enlightened postmodern undergrad