“There is no character, howsoever good and fine, but it can be destroyed by ridicule, howsoever poor and witless.” — Mark Twain

When President Donald Trump used his Twitter feed to intimidate the former ambassador to Ukraine while she was testifying before the House Intelligence Committee, his malign intent was more obvious than his rhetorical strategy. “Everywhere Marie Yovanovitch went turned bad,” he typed. “She started off in Somalia, how did that go?” Under the circumstances, it’s easy to see the attempt to bully the witness, more difficult to note the undercurrent of ridicule in the rhetorical mock-question: “how did that go?”

Progressives are so disgusted with Trump in general that they find it almost impossible to watch or listen to him. When he appears on their screens, their instinct is to turn to another station or mute the voice. In the area of humor in particular, progressives don’t think there’s anything funny about a man who embraces dictators, weakens environmental regulations and separates children from their parents.

If what we mean by “nothing funny” is that these destructive policies should not be laughed off, then this is correct. But if you assume that humor in general is positive and beneficial, and if you have never watched one of Trump’s frequent rallies, then you are missing the constant laughter from the audience that signals their amusement and approval. Understanding their seemingly unimpeachable loyalty to Trump requires an awareness of how this humor operates.

The first thing to notice is that Trump, perhaps on the theory that he knows more about humor than professional joke writers, relies heavily on blunt ridicule based on renaming people he despises. To take a few of these at random, recent jibes like Shifty (Adam) Schiff, Nervous Nancy (Pelosi), Sleepy Joe (Biden), Little Michael Bloomberg and (Mayor Pete) Boot-Edge-Edge remind us of such classics as Crooked Hillary, Lyin’ Ted (Cruz), Cheatin’ Obama and Low Energy Jeb (Bush).

Although they are far from clever, these rebrandings manage to highlight a single trait Trump wants to attach to the people he scorns. Like fans at a concert of an aging rock star, his audiences are delighted to hear the old hits and thrilled by new ones he serves up.

These crude insults have all the cleverness and maturity of schoolyard taunting, hovering just one step up from using someone’s name in the “banana-fana” “Name Game” song. In his landmark study “Jokes and Their Relation to the Unconscious,” Sigmund Freud pointed out that joking is often an indirect way of expressing hostility: that, instead of hitting someone, a joker can work criticism into a clever quip about them. As children mature, they learn how to use their wits rather than their fists to put someone down figuratively, not literally.

Having failed to achieve this kind of subtlety, bullies eschew nuanced joking in favor of stark ridicule. We should see Trump and his base in this light. As it happens, the relationship between bullying jokers and onlookers has been studied, and the findings explain part of Trump’s appeal. In studies of how observing ridicule affects social conformity, Leslie M. Janes and James M. Olson — psychologists at University College Brescia and the University of Western Ontario — identified a phenomenon they called “jeer pressure”: the increased desire to go along with a bully who not only attacks but also mocks his victims. Conditioned to conform to social norms in order to avoid being ridiculed themselves, such onlookers are likely to feel less empathy than they might otherwise for bullied but not ridiculed victims.

From the 1980s on, Rush Limbaugh pioneered this blend of outrage and ridicule in his depressingly effective rise to power and influence on the right. Terms like “feminazis,” “Drive-by Media” and “environmental wackos” took their place in his catalog of effectively fallacious rhetorical strategies alongside nicknames like Bela Pelosi, Osama-Obama, Algore (pronounced as a single word), and senators Chuck-U Schumer and Dick Turban. Like the bully’s attempt to garner support with anything but facts and logic, Limbaugh’s use of “rage-icule” boosted his popularity while distracting attention from pressing problems. Note that denigrating environmentalists does nothing to counter the climate crisis.

Another feature of public mockery deserves attention: People tend to enjoy jokes that make fun of individuals and groups they do not identify with. For this reason, the ongoing mockery of Trump by late-night comedians amuses progressives but not Trump loyalists, who are as likely to turn away from it as progressives are to shut their ears to the president’s taunting. Far from bringing us together, dueling senses of humor appreciation mark the divisions ripping America apart. That Trump uses hostile humor to build walls between these divisions is a significant, strategic and reprehensible use of his (rarely other than) bully pulpit.

Paul Lewis is the author of “Cracking Up: American Humor in a Time of Conflict.” This column originally appeared in the Chicago Tribune.