It is hard to navigate the rules of acceptability in public discourse these days, largely because the rules are different depending on who is speaking and what they are speaking about.

For example, Sean Spicer got into trouble when he condemned Syrian President Bashar al-Assad too strongly. Until last week, the problem with the Trump administration was that it was soft on Assad. After bombing the country, President Trump received accolades from Washington and the media establishment, which were now willing to embrace him as a serious leader who knows how to throw his weight around.

But Press Secretary Spicer put his foot in it when he heaped scorn on Assad, saying that in World War II, “someone as despicable as Hitler … didn’t even sink to using chemical weapons.” Immediately Spicer was labeled a Holocaust denier, and professional humanitarians and other right-thinkers demanded his resignation.

In the context of what we might call “conventional chemical weaponry,” what Spicer said is perfectly true. It is a frequently cited irony of the Second World War that, despite its carnage, brutality, and staggering civilian death toll, neither side resorted to using mustard gas or other chemical agents while bombing the other. The Nazis were prepared to use nerve gases to repel Allied advances, but were aware that the U.S. was ready to respond in kind, but more intensively.

Obviously the Nazis made ample use of chemical agents in murdering civilians in their extermination camps. But it is clear from Spicer’s comments that he understood the difference, and that he was not denying the existence of the gas chambers.

What Spicer was doing was playing the familiar game where Hitler is the gold standard of evil, and all officially bad people are held up and inspected for their similarity to him. The problem, as Spicer found out, is that while you are allowed to compare your enemies to Hitler as much as you like, and to show how close they come to being like Hitler, you are not allowed to suggest that anyone is as evil as Hitler, much less worse than Hitler.

Just as Muslims believe that Allah has no partner, that there is nothing like Allah, and that all and any comparisons are odious, so in the liberal pantheon of evil, Hitler stands alone. No one may suggest that anyone is worse than Hitler, because that would dissolve the categories of good and evil on which the entire world order is built.

Of course, there are exceptions to every rule. There is one person who is acceptably considered worse than Hitler, or at least potentially so—Donald Trump.

Kevin Dutton, an Oxford psychologist who claims expertise in psychopathology, made news last year when he announced that, according to his analytic use of the Psychopathic Personality Inventory (Revised), Donald Trump is more psychopathic than Hitler … by two points. Dutton’s clinical research was conducted through consultation with “an anonymous, highly respected and seasoned political correspondent,” and was thus objective and rigorous enough to be reported in dozens of media outlets, including Scientific American.

But for the less technically minded among us, we can look to Gossip Girl actress Leighton Meester, who observed that, were she to possess the power of time travel, she would no longer go back in time to kill Hitler, but would instead try to prevent Trump’s election. “Like, if I could snap my fingers? Trump would not be elected. That’s all,” Meester told Yahoo Style. “As of right now, I feel that way. Before Trump, I would have said that Hitler was never born.”

Comedian Louis C.K. also drew a stark parallel between Trump and Hitler, saying “the guy is Hitler.” Louis C.K. demurred from saying that Trump is actually worse than Hitler, however, preferring to say that they are just equivalently bad. Author Shalom Auslander, writing in the Washington Post, took a stronger view, begging us not to draw a comparison between Trump and Hitler, “because, frankly, it belittles Adolf Hitler.”

And of course, the “Trump ≥ Hitler” theme is a constant among the hollering class, and appears on signs and banners at every protest, anywhere in the country. Someone needs to get next to Sean Spicer and explain to him that, in the current calculus of evil, it is okay to say that Assad or any other official bad guy asymptotically approaches Hitler, but only one person, Spicer’s boss, actually crosses that axis.​

Seth Barron is associate editor of City Journal.