Racial Terminology (trigger warning)

I'm gearing up to begin the racism unit in my Social Problems course. Coincidentally, I'm also painfully trying to make my way through The Birth of a Nation. I'm about two-thirds through, right now, and it occurred to me that it might be useful in my class to have the students think about how racial terminology has shifted over time as the concept of race has shifted. Here is an Ngram for several terms for the "black" racial category:

(NOTE: the hyphenate terms don't bring any returns; "black," because it has several definitions, cannot be compared to these other terms; use of "Afro American" peaks in the late-1970s and then again in the late-1990s, but it never approached the frequency of usage of the other terms as is evident above.)

Three things jump out at me. First, use of both "nigger" and "negro" peak during the Civil War and after/at the tail end of the Civil Rights Movement; however, the former has until recently been dwarfed by the use of the latter. Second, the N-word has remained surprisingly consistent in its use from the mid-1800s on. Finally, "African American" developed much later than I would have guessed.

My only concern in using this in class is that it might play into some misleading notions of "political correctness." Otherwise, I think it might be helpful to show that, since language reflects meaning and since language changes over time, the seemingly static nature of "race" has changed quite a bit.