The President of the United States called someone a “dog” on Twitter Tuesday morning, another first for his debasement of Presidential rhetoric. It is, sadly, not a surprise. “Dog” has long been one of Trump’s favorite Twitter insults, and he is the first President in more than a hundred years not to have a dog as a pet in the White House. (Trump once told his biographer Tim O’Brien that he considered all animals “germy.”) A more or less complete list of those he has attacked with this label, just since his entry into national politics in 2015, includes: Mitt Romney, the 2012 Republican Presidential nominee, who “choked like a dog”; David Gregory, the former host of “Meet the Press,” “fired like a dog!”; Chuck Todd, Gregory’s replacement as “Meet the Press” host, “who will be fired like a dog”; Ted Cruz, one of Trump’s opponents in the 2016 Republican primary, who “lies like a dog—over and over again”; Ted Cruz’s former communications director, “fired like a dog”; Brent Bozell, the conservative columnist at National Review, who “came to my office begging for money like a dog”; Erick Erickson, the anti-Trump conservative blogger, “fired like a dog”; Glenn Beck, the former Fox TV host, also “fired like a dog”; George Will, the conservative Washington Post columnist, “thrown off ABC like a dog!”; and Arianna Huffington, the liberal-Web-site founder, “a dog who wrongfully comments on me.”

But all of those tweets, as intemperate as they were, were made before Trump actually became the President. Yes, he complained last October that the Tennessee senator Bob Corker, one of his few remaining public critics in the Republican Party, could no longer get elected “dog catcher.” And Trump has hurled playground taunts at a breathtakingly long line of targets during his eighteen months in office, from African-American football players to the Prime Minister of Canada. But, for whatever reason, Trump had restrained himself from using what is clearly one of his favorite insults until 7:31 A.M. on Tuesday: “When you give a crazed, crying lowlife a break, and give her a job at the White House, I guess it just didn’t work out. Good work by General Kelly for quickly firing that dog!”

The precipitating cause of the President’s Twitter rant was the betrayal by his former television protégée turned White House adviser, Omarosa Manigault Newman, whose new memoir, “Unhinged,” recounts scenes of Trump White House madness throughout his troubled first year in office. In the course of her book tour, Manigault Newman has revealed, on live television, what she says are secretly taped conversations with Trump and the White House chief of staff John Kelly as he was firing her in the White House Situation Room. The accusations seem to have stunned Trump, who first called her a “lowlife” during a Presidential photo op on Friday (very likely another first in the annals of rhetorical taboos broken by the forty-fifth President), and who seemed to believe that she, like his legions of other fired and forced-out former aides, would remain silent under the terms of the legally dubious nondisclosure agreements they have been forced to sign.

The tweet exploded like a bomb on Twitter, where many immediately labelled it as racist and sexist (and noted that it came after Manigault Newman alleged that there were recordings of Trump using the N-word during tapings of his TV show “The Apprentice”). Trump has undoubtedly been on an awful recent streak of insulting African-Americans who dare to oppose him, from calling Don Lemon, a black CNN anchor, “the dumbest man on television” to questioning the intelligence of the N.B.A. star LeBron James and the Democratic congresswoman Maxine Waters. And so, once again, we are left with a public debate over just how low Trump has sunk: until now, Trump has used the Twitter insult “dog” to demean primarily white men. What did he mean by applying it to an African-American woman? Was he being racist, sexist, some toxic combination of the two? Or merely horrible? As Manigault Newman herself wondered in an interview on MSNBC after Trump’s tweet, “If he would say that publicly, what else would he say about me privately? He has no respect for women, for African-Americans.” The White House response is to lamely point out, as the press secretary, Sarah Huckabee Sanders, did Tuesday, that Trump is “equal opportunity” in his insults.

Either way, Trump’s tweet makes Omarosa more sympathetic than she otherwise would be. She had been one of the more loathed characters on his “Apprentice” television shows, and she was reportedly deeply unpopular in the White House. Probably no one other than Trump himself thought she was a good hire for the West Wing. Her kiss-and-tell memoir reeks with the distasteful Washington tradition of cashing in on brief and undistinguished service at the expense of the President who appointed you. Her admission that she surreptitiously tape-recorded conversations in the White House—in the super-secure Situation Room, of all places—would normally be the subject of sharp criticism. And yet Trump’s tweets have brought the focus back on himself and left her as the latest victim of his bullying.

I’m going to type it out one more time: the President of the United States called someone a “dog” on Twitter Tuesday morning. I wasn’t surprised, and, as appalling as it was, the early-morning tweet wasn’t treated by most Web sites and cable-news operations as the top news of the day. Those tended to focus on the arbitration case that Trump’s 2016 campaign filed against Manigault Newman for allegedly violating her nondisclosure agreement or the about-to-conclude money-laundering trial of Trump’s former campaign chairman, Paul Manafort, who may be so confident in a Presidential pardon that his defense has rested without even mounting a case or calling any witnesses. But are we so numb to Trump’s rhetorical outrages that we can’t still be a little bit horrified by them? Omarosa titled her kiss-and-tell “Unhinged.” Trump seems intent on proving her right.