There should be no mystery as to why President Trump’s verbal assaults against African American reporters, candidates, lawmakers and athletes are cloaked in language that characterizes African Americans as unintelligent, untrustworthy and unqualified, as The Post reported Saturday. When it comes to dealing with African Americans, Trump adheres to the racial etiquette of Jim Crow America.

The Jim Crow system of racial segregation, in addition to anti-black laws on the books, dictated the rituals of behavior that black people were expected to follow — how to act, speak and behave — in the presence of white people. And Jim Crow racial etiquette prescribed the manners and attitudes that whites were to adopt when interacting with blacks.

Jim Crow racial etiquette rested on the belief — no, make that conviction — that white people were superior to blacks in intelligence and social status. Hence Trump’s way with black women and men.

Among the guides of behavior: Never treat black people as equals. Don’t let them think for one second that they are anything other than second-class Americans.

The means of getting that point across — followed faithfully by Trump — is in the use of words. Words that convey disrespect. Words that are put-downs. Words that make it clear that blacks, regardless of rank and station, must never assume an air of equality with a white man, must never impute that a white person is dishonorable, lying or capable of moral corruption.

Thus, Trump’s response to a well-grounded question by seasoned CNN correspondent Abby Phillip, who is black: “What a stupid question. … But I watch you a lot. You ask a lot of stupid questions,” he told her at the White House this week.

At a Wednesday news conference at the White House, Trump ordered American Urban Radio Networks’ April Ryan, an African American, to “sit down.” Outside the White House on Friday, he called her “nasty” and a “loser.”

And Trump’s description this summer of CNN’s veteran TV host Don Lemon, also African American? The “dumbest man on television.”

Rep. Frederica Wilson (D-Fla.), an African American, is “wacky,” and former Trump aide Omarosa Manigault Newman is a “dog.” Trump brands a question from “PBS NewsHour” White House correspondent Yamiche Alcindor, an African American, about his rhetoric and its possible encouragement to white nationalists “a racist question.”

Of all the words from which to choose, Trump declared Georgia gubernatorial candidate Stacey Abrams — magna cum laude at Spelman College, master of public policy at the University of Texas, Yale law degree, former Atlanta deputy city attorney, 10 years in Georgia House of Representatives, including a stretch as minority leader — to be “not qualified.” Maxine Waters (Calif.), a senior House Democrat, is a “low-IQ person,” said Trump.

And Florida gubernatorial candidate and Tallahassee’s African American mayor, Andrew Gillum, is, in Trump’s word, a “thief.”

That is what Jim Crow etiquette prescribes — belittle and demean blacks, put them in their place, make clear that they are not equal socially, morally or brain-wise.

And it demands that whites never treat blacks with courtesy — lest they get the wrong impression and start acting uppity. The only conduct allowable for blacks, when in the company of whites, is to be agreeable and undemanding.

Those have been shown to be Trump’s standards of behavior, his rules of racial etiquette. Straight out of Jim Crow.

Read more:

Erik Wemple: Black, female and covering President Trump? Expect peak nasty.

Jonathan Capehart: Yes, Donald Trump, you are a ‘racist’

Jennifer Rubin: Like his lies, Trump’s racist comments don’t surprise, but they should be counted

Susan Estrich: Don’t let Trump get away with his racist ad

Paul Waldman: Why do all these racists keep joining the GOP?