The real story does have a natural “Big Crash / Midpoint Disaster / Lowest Point” for both LBJ and MLK: The first bridge crossing, which King misses, leads to horrific violence on national TV, mortifying Johnson. But DuVernay wants more, so she takes an event that only kind of really happened and inserts it here.
The change involves King’s reason for missing the march. The big crash usually happens because of the hero’s flaw, forcing them to confront it for the first time. The real reason King missed the march speaks to one of King’s potential flaws, but DuVernay created a different reason that speaks to another flaw.
In the true story, King felt he had to stay home in Atlanta and preach to his congregation, so he planned to join the marchers later (There are some suspicions that his father, who was his co-preacher, suspected that there would be violence, feigned illness and asked King to make sure be there to preach.)
If DuVernay had kept this reason, would that speak to a flaw of King’s? Well, it’s a controversial thing to say, but sort of. In fact, DuVernay does come close to making this criticism elsewhere. It’s hard not to notice that King keeps missing the violence: He’s not at the night march where Jimmie Lee Jackson gets killed, he misses the first bridge crossing, and he turns back the second bridge crossing when he sees the cops, disappointing everybody. It feels awful to criticize a man who would soon give his life for the movement, but in this campaign, he kind of looks like someone who is willing to put others in danger but not himself.
But DuVernay decides to bring in another of King’s flaws here instead. To do so, she must do some fictionalization, creating an event that didn’t really happen …but basically happened. In the movie, King is stuck at home dealing with a marital crisis.
It’s true that J. Edgar Hoover was an employee of Johnson’s, and while working “under” Johnson recorded King having affairs and mailed those tapes to Coretta who then confronted her husband. That really happened. But Hoover didn’t really do it at this point in history, and Johnson probably never knew he was going to do it. Hoover was totally rogue by this point, and historians believe that Johnson only kept him on because Hoover was blackmailing him. Certainly, whenever it happened, it was not Johnson’s attempt to stop events in Selma.
This is obviously a big point in favor of the case that DuVernay is unfair to Johnson, but is it really? Johnson should have known this was happening and should have stopped it. It’s only fair to show that the Johnson administration, in the person of an employee Johnson refused to rein in, was viciously attacking King’s marriage, so it’s fair to include that in a movie about King’s relationship with Johnson, even if history has to be rearranged and Johnson’s sin of omission turned into a sin of commission.
And it certainly works in terms of creating an effective lowest point for both protagonists. Johnson hits a moral low point, making his eventual moral redemption more powerful. King suffers greatly, is forced to admit his worst behavior, and feels even guiltier when the problems results in his missing the violent march. (But it is awkward that King’s adultery is neither set up beforehand nor paid off afterwards: We never see him commit adultery beforehand nor refuse to do it afterwards.)
Basically, the best reason to insert this moment is to include King’s biggest flaw and one of Johnson’s biggest flaws into this story, so that the portrait of each man will be more complete and complicated, even if these two flaws didn’t actually play a big part in this particular event. DuVernay is being true to history on a broader scale even if it means fictionalizing this event. I can accept that.