George Washington Williams (Samuel L. Jackson) is shoehorned into this movie to make sense of the white savior, Tarzan.
"Hopefully with this movie, we can persuade people to look into George Washington Williams’ story and, through him, find out about that first holocaust in the Congo."
"For many years, he was thought to be an evil spirit, a ghost in the trees." So you might imagine, "he" being Tarzan (Alexander Skarsgård), who used to swing on vines and take dire revenge on Africans who hunted members of his ape family. But now, with Tarzan himself on hand, black tribespeople in Congo are singing the "Legend of Tarzan", celebrating their favorite white guy, just returned from London for a visit.
It's helpful that Tarzan's wife Jane (Margot Robbie) is on hand to translate the song in this movie that's also titled The Legend of Tarzan. Even if you've heard this story before, their traveling companion, George Washington Williams (Samuel L. Jackson), has not, and so he's ready to be impressed, as much by the happy reverence displayed by the black folks as by all the king of the jungle business. Which is to say, George has a particular interest in the singers, whom he's determined to save from being kidnapped by white slavers.
The slavery plot is not part of the legend as it's sung, but has been inserted into the movie, via George. A few scenes earlier, he visits Tarzan in London, where the ape-man has lived for some 20 years, delivered from the dark continent where he spent his childhood into the privilege afforded him as Lord Greystoke. Around 1890, as this movie has it, George brings news of the illegal slave trade being conducted by Belgian King Leopold, a means to finance his railroad, which in turn supports his diamond mining. Though Tarzan resists returning to Africa, he agrees when pressed on this ethical and political point, providing the movie with an anti-colonialist revisionist foundation, which is laid out awkwardly by a series of opening title cards.
These cards don't mention that George -- unlike Edgar Rice Burroughs' fantastical Tarzan -- is based on a real life figure. So is their primary adversary, the sinister Léon Rom (Christoph Waltz), head of Leopold's barbarous Force Publique. Both George and Rom have particular interests in Tarzan, owing to his celebrity. George's is righteous, if complicated: enlisting Tarzan to stop the slavers, he hopes also to redeem his own grisly past, as a 14-year-old Union Civil War soldier and then a mercenary in the genocidal Indian Wars. Rom's aim is more mundane; that is, to secure his personal fame and fortune, along the way murdering people indiscriminately, sometimes with a rosary-like device he claims was given him by a priest when he was a child (this allows for some homophobic innuendo associated with his villainy).
Rom's crude exploitations might offset the other white characters' ignorance (making Jane and Tarzan look relatively innocent), but the movie makes clear that George is its moral conscience. He educates Tarzan and Jane (who remains nostalgic about Congo (where she "grew up") as to the colonialists' abuses of the continent (for rubber, minerals, diamonds, and humans). But George is not only a black man endeavoring to do a right thing. He's shoehorned into this movie to make the white savior Tarzan make even a modicum of sense in a universe where he can't possibly -- namely, today's universe.
Who thought this was a good idea? While the white leads serve their generic purposes -- Tarzan talking to CGIed animals and Jane playing the spunky "damsel" (her self-aware word for it, when Rom kidnaps her and chains her to a steamboat railing for half the movie) -- George is indeterminably more interesting than any of these white folks. Part of that has to do with Jackson's performance, even if you might anticipate his perfectly timed glare or thunderous pronouncement. But it also has to do with the wrench George throws into the movie's most common white guy delusions, say, the noble man-beast or the white liberator.
The problem -- it's a big one -- is that George is the sidekick here. Where he achieves what the real-life Williams set out to do, going to Congo to document white European atrocities, to forge a legal framework for stopping them, too often, George is rendered comic relief, cracking wise or barely keeping up with the prodigiously worked-out Tarzan, arriving at a scene just in time to catch his breath, cock his gun, and traipse off again after the great white specimen. When at last George essentially stops the action to tell his own history, Tarzan listens quietly to what might have been a sequel to The Hateful Eight, in which Jackson's Major Marquis Warren not only survives but also finds remedy for what seems to be the world's forever-slavery, an apparently unkillable institution and idea. As George concludes recounting his evil deeds working for white men, he observes, "We ain't better than these Belgians."
If George sees the problem, the movie can't quite sort out who "we" might be. That's not to say George doesn't try, repeatedly. While Tarzan takes up screen time with many stunts and snarly confrontations with Rom (and one prolonged slam-and-bam MMA-style fight with a gorilla brother), he's also got a conflict to resolve with a Congolese chief, Mbonga (Djimon Honsou), one that goes back decades. At the moment of this big showdown, surrounded by Mbonga's armed men and Tarzan's ape family, George again arrives late. He watches, horrified, then steps into the middle of the fight to point out that their shared enemy is that nebulous "we".